### 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)

parser->push_warning(member.variable, GDScriptWarning::GET_NODE_DEFAULT_WITHOUT_ONREADY, is_using_shorthand ? "$" : "get_node()");
						}
					}
				}
#endif
			} break;
			case GDScriptParser::ClassNode::Member::CONSTANT: {
				check_class_member_name_conflict(p_class, member.constant->identifier->name, member.constant);
				member.constant->set_datatype(resolving_datatype);
				resolve_constant(member.constant, false);
				
				for (GDScriptParser::AnnotationNode *&E : member.constant->annotations) {
					resolve_annotation(E);
					E->apply(parser, member.constant);
				}
			} break;
			case GDScriptParser::ClassNode::Member::SIGNAL: {
				check_class_member_name_conflict(p_class, member.signal->identifier->name, member.signal);
				member.signal->set_datatype(resolving_datatype);
				
				
				MethodInfo mi = MethodInfo(member.signal->identifier->name);
				for (int j = 0; j < member.signal->parameters.size(); j++) {
					GDScriptParser::ParameterNode *param = member.signal->parameters[j];
					GDScriptParser::DataType param_type = type_from_metatype(resolve_datatype(param->datatype_specifier));
					param->set_datatype(param_type);
					mi.arguments.push_back(PropertyInfo(param_type.builtin_type, param->identifier->name));
					
				}
				member.signal->set_datatype(make_signal_type(mi));