### 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)

return; 
			}
			
			
			if (p_identifier->source == GDScriptParser::IdentifierNode::UNDEFINED_SOURCE || p_identifier->source == GDScriptParser::IdentifierNode::MEMBER_CONSTANT) {
				return;
			}
			GDScriptParser::FunctionNode *function_test = lambda_stack.back()->get()->function;
			
			
			while (function_test != nullptr && function_test != p_identifier->source_function && function_test->source_lambda != nullptr && !function_test->source_lambda->captures_indices.has(p_identifier->name)) {
				function_test->source_lambda->captures_indices[p_identifier->name] = function_test->source_lambda->captures.size();
				function_test->source_lambda->captures.push_back(p_identifier);
				function_test = function_test->source_lambda->parent_function;
			}
		}
		return;
	}
	StringName name = p_identifier->name;
	p_identifier->source = GDScriptParser::IdentifierNode::UNDEFINED_SOURCE;
	
	
	Variant::Type builtin_type = GDScriptParser::get_builtin_type(name);
	if (builtin_type != Variant::OBJECT && builtin_type < Variant::VARIANT_MAX) {
		if (can_be_builtin) {
			p_identifier->set_datatype(make_builtin_meta_type(builtin_type));
			return;
		} else {
			push_error(R"(Builtin type cannot be used as a name on its own.)", p_identifier);
		}