### 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)

case GDScriptParser::ClassNode::Member::VARIABLE: {
					if (is_base && (!base.is_meta_type || member.variable->is_static)) {
						p_identifier->set_datatype(member.get_datatype());
						p_identifier->source = member.variable->is_static ? GDScriptParser::IdentifierNode::STATIC_VARIABLE : GDScriptParser::IdentifierNode::MEMBER_VARIABLE;
						p_identifier->variable_source = member.variable;
						member.variable->usages += 1;
						return;
					}
				} break;
				case GDScriptParser::ClassNode::Member::SIGNAL: {
					if (is_base && !base.is_meta_type) {
						p_identifier->set_datatype(member.get_datatype());
						p_identifier->source = GDScriptParser::IdentifierNode::MEMBER_SIGNAL;
						return;
					}
				} break;
				case GDScriptParser::ClassNode::Member::FUNCTION: {
					if (is_base && (!base.is_meta_type || member.function->is_static)) {
						p_identifier->set_datatype(make_callable_type(member.function->info));
						return;
					}
				} break;
				case GDScriptParser::ClassNode::Member::CLASS: {
					reduce_identifier_from_base_set_class(p_identifier, member.get_datatype());
					return;
				}
				default: {
					
				}
			}