### Godot version

v4.0.rc1.official [8843d9ad3]

### System information

Lubuntu

### Issue description

You can't use + or += to mutate typed arrays.

It seems to be not correctly getting the type information from the second operand.

An erudite poster on the discord puts it differently:
> it's more like operator + doesn't retain Array typing
> the syntax for Array Concatenation via operators, but the idea gets across i think


The error you see is:
```Trying to assign an array of type "Array" to a variable of type "Array[int]".```


### Steps to reproduce

```
	var Alice: Array[int] = [1,2,3]
	var Bob: Array[int] = [4,5,6]
	Alice += Bob
```
This will crash with the above error message.

### Minimal reproduction project

[plus_syntax_broken_demo_project.zip](https://github.com/godotengine/godot/files/10694514/plus_syntax_broken_demo_project.zip)

p_source = p_function;
	}
	StringName function_name = p_function->identifier != nullptr ? p_function->identifier->name : StringName();
	if (p_function->get_datatype().is_resolving()) {
		push_error(vformat(R"(Could not resolve function "%s": Cyclic reference.)", function_name), p_source);
		return;
	}
	if (p_function->resolved_signature) {
		return;
	}
	p_function->resolved_signature = true;
#ifdef DEBUG_ENABLED
	HashSet<GDScriptWarning::Code> previously_ignored_warnings = parser->ignored_warnings;
	for (GDScriptWarning::Code ignored_warning : p_function->ignored_warnings) {
		parser->ignored_warnings.insert(ignored_warning);
	}
#endif
	GDScriptParser::FunctionNode *previous_function = parser->current_function;
	parser->current_function = p_function;
	bool previous_static_context = static_context;
	static_context = p_function->is_static;
	GDScriptParser::DataType prev_datatype = p_function->get_datatype();
	GDScriptParser::DataType resolving_datatype;
	resolving_datatype.kind = GDScriptParser::DataType::RESOLVING;
	p_function->set_datatype(resolving_datatype);
#ifdef TOOLS_ENABLED
	int default_value_count = 0;
#endif 
	for (int i = 0; i < p_function->parameters.size(); i++) {
		resolve_parameter(p_function->parameters[i]);