### 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)

bool has_valid_setter = false;
				if (member.variable->getter_pointer != nullptr) {
					if (p_class->has_function(member.variable->getter_pointer->name)) {
						getter_function = p_class->get_member(member.variable->getter_pointer->name).function;
					}
					if (getter_function == nullptr) {
						push_error(vformat(R"(Getter "%s" not found.)", member.variable->getter_pointer->name), member.variable);
					} else {
						GDScriptParser::DataType return_datatype = getter_function->datatype;
						if (getter_function->return_type != nullptr) {
							return_datatype = getter_function->return_type->datatype;
							return_datatype.is_meta_type = false;
						}
						if (getter_function->parameters.size() != 0 || return_datatype.has_no_type()) {
							push_error(vformat(R"(Function "%s" cannot be used as getter because of its signature.)", getter_function->identifier->name), member.variable);
						} else if (!is_type_compatible(member.variable->datatype, return_datatype, true)) {
							push_error(vformat(R"(Function with return type "%s" cannot be used as getter for a property of type "%s".)", return_datatype.to_string(), member.variable->datatype.to_string()), member.variable);
						} else {
							has_valid_getter = true;
#ifdef DEBUG_ENABLED
							if (member.variable->datatype.builtin_type == Variant::INT && return_datatype.builtin_type == Variant::FLOAT) {
								parser->push_warning(member.variable, GDScriptWarning::NARROWING_CONVERSION);
							}
#endif
						}
					}
				}
				if (member.variable->setter_pointer != nullptr) {
					if (p_class->has_function(member.variable->setter_pointer->name)) {
						setter_function = p_class->get_member(member.variable->setter_pointer->name).function;