re-add gjs to DEFAULT_FLOAT_RULES

[n3m0-22]

This is to fix #1608 which affects Wayland, and was caused by #1605.

#1605 fixed #1056 by moving gjs from DEFAULT_FLOAT_RULES to SKIPTASKBAR_EXCEPTIONS.

By keeping gjs in both it appears to resolve both issues.

To test in X11:

• install https://extensions.gnome.org/extension/4337/desktop-icons-neo/
• right click on the Desktop and select Desktop Icon Settings
• with Desktop Icon Settings window open Alt + Tab

There should not be any blank gjs icon showing.

To test in Wayland:

• while logged into Wayland enable tiling
• open a window on the first workspace
• open a window on the second workspace

Both should now take up the whole workspace and not just half as described in #1608.

[leviport]

Can confirm, this fixes empty tiles in Wayland. I can still make the bug happen if I hit Super + G after logging in, then opening some apps, but that isn't a surprise.