### Godot version

4.0 stable

### System information

Fedora, RX 590

### Issue description

I made a dictionary, and instead of using `:` to separate between key and value, i accidentally used `=`.
The error message was not clear at all `Parse Error: Expected identifier or string as LUA-style dictionary key.` 

I don't think assuming that people know how dictionaries are made in LUA is reasonable. And if this is not about LUA the programming language, i don't even know what this is about :D

I think this error should be replaced with something of the sort "Please use `:` as separator instead of `=` in your dictionary"

### Steps to reproduce

Paste this code in a script:

```

var dict = {
	1 = "lala"
}
```

Observe the error message
![image](https://user-images.githubusercontent.com/7917475/224549538-38ea25aa-ba75-431e-868b-0733a53b90ad.png)


### Minimal reproduction project

see above
{ nullptr,                                          nullptr,                                        PREC_NONE }, 
		{ &GDScriptParser::parse_await,                  	nullptr,                                        PREC_NONE }, 
		{ nullptr,                                          nullptr,                                        PREC_NONE }, 
		{ nullptr,                                          nullptr,                                        PREC_NONE }, 
		{ nullptr,                                          nullptr,                                        PREC_NONE }, 
		{ nullptr,                                          nullptr,                                        PREC_NONE }, 
		{ nullptr,                                          nullptr,                                        PREC_NONE }, 
		{ nullptr,                                          nullptr,                                        PREC_NONE }, 
		{ &GDScriptParser::parse_lambda,                    nullptr,                                        PREC_NONE }, 
		{ nullptr,                                          &GDScriptParser::parse_binary_operator,      	PREC_CONTENT_TEST }, 
		{ nullptr,                                          &GDScriptParser::parse_type_test,            	PREC_TYPE_TEST }, 
		{ nullptr,                                          nullptr,                                        PREC_NONE }, 
		{ &GDScriptParser::parse_preload,					nullptr,                                        PREC_NONE }, 
		{ &GDScriptParser::parse_self,                   	nullptr,                                        PREC_NONE }, 
		{ nullptr,                                          nullptr,                                        PREC_NONE }, 
		{ nullptr,                                          nullptr,                                        PREC_NONE }, 
		{ &GDScriptParser::parse_call,						nullptr,                                        PREC_NONE }, 
		{ nullptr,                                          nullptr,                                        PREC_NONE }, 
		{ nullptr,                                          nullptr,                                        PREC_NONE }, 
		{ nullptr,                                          nullptr,                                        PREC_NONE }, 
		{ &GDScriptParser::parse_yield,                     nullptr,                                        PREC_NONE }, 
		
		{ &GDScriptParser::parse_array,                  	&GDScriptParser::parse_subscript,            	PREC_SUBSCRIPT }, 
		{ nullptr,                                          nullptr,                                        PREC_NONE }, 
		{ &GDScriptParser::parse_dictionary,             	nullptr,                                        PREC_NONE }, 
		{ nullptr,                                          nullptr,                                        PREC_NONE }, 
		{ &GDScriptParser::parse_grouping,               	&GDScriptParser::parse_call,                 	PREC_CALL }, 
		{ nullptr,                                          nullptr,                                        PREC_NONE }, 
		{ nullptr,                                          nullptr,                                        PREC_NONE }, 
		{ nullptr,                                          nullptr,                                        PREC_NONE },