### 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)

if (src_class == p_target.class_type || src_class->fqcn == p_target.class_type->fqcn) {
					return true;
				}
				src_class = src_class->base_type.class_type;
			}
			return false;
		case GDScriptParser::DataType::VARIANT:
		case GDScriptParser::DataType::BUILTIN:
		case GDScriptParser::DataType::ENUM:
		case GDScriptParser::DataType::RESOLVING:
		case GDScriptParser::DataType::UNRESOLVED:
			break; 
	}
	return false;
}
void GDScriptAnalyzer::push_error(const String &p_message, const GDScriptParser::Node *p_origin) {
	mark_node_unsafe(p_origin);
	parser->push_error(p_message, p_origin);
}
void GDScriptAnalyzer::mark_node_unsafe(const GDScriptParser::Node *p_node) {
#ifdef DEBUG_ENABLED
	if (p_node == nullptr) {
		return;
	}
	for (int i = p_node->start_line; i <= p_node->end_line; i++) {
		parser->unsafe_lines.insert(i);
	}
#endif
}
void GDScriptAnalyzer::downgrade_node_type_source(GDScriptParser::Node *p_node) {