### 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(p_assignable, GDScriptWarning::INFERENCE_ON_VARIANT, p_kind);
			}
#endif
		} else {
			if (!initializer_type.is_set()) {
				push_error(vformat(R"(Could not resolve type for %s "%s".)", p_kind, p_assignable->identifier->name), p_assignable->initializer);
			}
		}
		if (!has_specified_type) {
			type = initializer_type;
			if (!type.is_set() || (type.is_hard_type() && type.kind == GDScriptParser::DataType::BUILTIN && type.builtin_type == Variant::NIL && !is_constant)) {
				type.kind = GDScriptParser::DataType::VARIANT;
			}
			if (p_assignable->infer_datatype || is_constant) {
				type.type_source = GDScriptParser::DataType::ANNOTATED_INFERRED;
			} else {
				type.type_source = GDScriptParser::DataType::INFERRED;
			}
		} else if (!specified_type.is_variant()) {
			if (initializer_type.is_variant() || !initializer_type.is_hard_type()) {
				mark_node_unsafe(p_assignable->initializer);
				p_assignable->use_conversion_assign = true;
				if (!initializer_type.is_variant() && !is_type_compatible(specified_type, initializer_type, true, p_assignable->initializer)) {
					downgrade_node_type_source(p_assignable->initializer);
				}
			} else if (!is_type_compatible(specified_type, initializer_type, true, p_assignable->initializer)) {
				if (!is_constant && is_type_compatible(initializer_type, specified_type)) {
					mark_node_unsafe(p_assignable->initializer);
					p_assignable->use_conversion_assign = true;
				} else {