### 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 (p_function->resolved_body) {
		return;
	}
	p_function->resolved_body = true;
#ifdef DEBUG_ENABLED
	HashSet<GDScriptWarning::Code> previously_ignored_warnings = parser->ignored_warnings;
	for (GDScriptWarning::Code ignored_warning : p_function->ignored_warnings) {
		parser->ignored_warnings.insert(ignored_warning);
	}
#endif
	GDScriptParser::FunctionNode *previous_function = parser->current_function;
	parser->current_function = p_function;
	bool previous_static_context = static_context;
	static_context = p_function->is_static;
	resolve_suite(p_function->body);
	if (!p_function->get_datatype().is_hard_type() && p_function->body->get_datatype().is_set()) {
		
		p_function->set_datatype(p_function->body->get_datatype());
	} else if (p_function->get_datatype().is_hard_type() && (p_function->get_datatype().kind != GDScriptParser::DataType::BUILTIN || p_function->get_datatype().builtin_type != Variant::NIL)) {
		if (!p_function->body->has_return && (p_is_lambda || p_function->identifier->name != GDScriptLanguage::get_singleton()->strings._init)) {
			push_error(R"(Not all code paths return a value.)", p_function);
		}
	}
#ifdef DEBUG_ENABLED
	parser->ignored_warnings = previously_ignored_warnings;
#endif
	parser->current_function = previous_function;
	static_context = previous_static_context;
}
void GDScriptAnalyzer::decide_suite_type(GDScriptParser::Node *p_suite, GDScriptParser::Node *p_statement) {