### 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)

return bad_type;
								}
								result = ref->get_parser()->head->get_datatype();
							} else {
								result = make_script_meta_type(member.constant->initializer->reduced_value);
							}
							found = true;
							break;
						}
						[[fallthrough]];
					default:
						push_error(vformat(R"("%s" is a %s but does not contain a type.)", first, member.get_type_name()), p_type);
						return bad_type;
				}
			}
		}
	}
	if (!result.is_set()) {
		push_error(vformat(R"(Could not find type "%s" in the current scope.)", first), p_type);
		return bad_type;
	}
	if (p_type->type_chain.size() > 1) {
		if (result.kind == GDScriptParser::DataType::CLASS) {
			for (int i = 1; i < p_type->type_chain.size(); i++) {
				GDScriptParser::DataType base = result;
				reduce_identifier_from_base(p_type->type_chain[i], &base);
				result = p_type->type_chain[i]->get_datatype();
				if (!result.is_set()) {
					push_error(vformat(R"(Could not find type "%s" under base "%s".)", p_type->type_chain[i]->name, base.to_string()), p_type->type_chain[1]);
					return bad_type;