Save button of FileDialog keeps disabled after changing file_mode.

[HolonProduction]

Godot version

v4.1.stable.official [9704596]

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