### 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)

}
					j++;
				}
				parent_signature += ") -> ";
				const String return_type = parent_return_type.is_hard_type() ? parent_return_type.to_string() : "Variant";
				if (return_type == "null") {
					parent_signature += "void";
				} else {
					parent_signature += return_type;
				}
				push_error(vformat(R"(The function signature doesn't match the parent. Parent signature is "%s".)", parent_signature), p_function);
			}
#ifdef DEBUG_ENABLED
			if (native_base != StringName()) {
				parser->push_warning(p_function, GDScriptWarning::NATIVE_METHOD_OVERRIDE, function_name, native_base);
			}
#endif
		}
#endif 
	}
	if (p_function->get_datatype().is_resolving()) {
		p_function->set_datatype(prev_datatype);
	}
#ifdef DEBUG_ENABLED
	parser->ignored_warnings = previously_ignored_warnings;
#endif
	parser->current_function = previous_function;
	static_context = previous_static_context;
}
void GDScriptAnalyzer::resolve_function_body(GDScriptParser::FunctionNode *p_function, bool p_is_lambda) {