### Godot version

v4.1.stable.official [970459615]

### System information

Windows 10

### Issue description

When changing the `file_mode` of `FileDialog` from "Open File" to "Save File" via code the "Save" button keeps disabled until a file or folder is selected if the "Open" button was disabled before.

Basically the button activity has to be updated when `file_mode` is changed. I have made the change already but the last time I opened an PR without an issue some people requested I open one. So here you are!

### Steps to reproduce

- Open the MRP and start it
- click anywere to open the dialog
- after 10 seconds the dialog changes file_mode
- if the button is disabled before the change it is as well after it

### Minimal reproduction project

[file_dialogue_test.zip](https://github.com/godotengine/godot/files/11991311/file_dialogue_test.zip)

return root_subfolder;
}
void FileDialog::set_mode_overrides_title(bool p_override) {
	mode_overrides_title = p_override;
}
bool FileDialog::is_mode_overriding_title() const {
	return mode_overrides_title;
}
void FileDialog::set_file_mode(FileMode p_mode) {
	ERR_FAIL_INDEX((int)p_mode, 5);
	if (mode == p_mode) {
		return;
	}
	mode = p_mode;
	switch (mode) {
		case FILE_MODE_OPEN_FILE:
			set_ok_button_text(RTR("Open"));
			if (mode_overrides_title) {
				set_title(TTRC("Open a File"));
			}
			makedir->hide();
			break;
		case FILE_MODE_OPEN_FILES:
			set_ok_button_text(RTR("Open"));
			if (mode_overrides_title) {
				set_title(TTRC("Open File(s)"));
			}
			makedir->hide();