fix: Explicitly specify D-Bus signal signature for Gnome clipboard events

[rohankmr414]

This pull request makes a small but important fix to the D-Bus signal connection logic in the GNOME clipboard server. The change ensures that the D-Bus signal signature is explicitly specified when connecting and disconnecting the ClipboardChanged signal, which is necessary for proper type matching in Qt6. This is required for clipboard history to work in GNOME 49

[aurelleb]

@dagimg-dot can you quickly test this on your side?
@rohankmr414 you say it's required for clipboard history to work but afaik it already works at the moment

[rohankmr414]

@aurelleb After I upgraded to Fedora 43, which also upgraded my GNOME version to 49, the clipboard history feature stopped working. I see this in the log line:

Feb 02 14:39:02 fedora vicinae[35494]: [14:39:02.273] INFO   -  Unloading command "clipboard.history"
Feb 02 14:39:18 fedora vicinae[35494]: [14:39:18.861] INFO   -  Unloading command "clipboard.history"

After the fix in the PR, when I start the server locally, I do see the following logs in the server, which were not showing up earlier

[14:45:17.947] INFO   -  Received new clipboard selection with 1 offers
[14:45:17.947] INFO   -  "text/plain" (size="6 bytes", password=false)

[dagimg-dot]

@aurelleb After I upgraded to Fedora 43, which also upgraded my GNOME version to 49, the clipboard history feature stopped working. I see this in the log line:

Feb 02 14:39:02 fedora vicinae[35494]: [14:39:02.273] INFO   -  Unloading command "clipboard.history"
Feb 02 14:39:18 fedora vicinae[35494]: [14:39:18.861] INFO   -  Unloading command "clipboard.history"

After the fix in the PR, when I start the server locally, I do see the following logs in the server, which were not showing up earlier

[14:45:17.947] INFO   -  Received new clipboard selection with 1 offers
[14:45:17.947] INFO   -  "text/plain" (size="6 bytes", password=false)

hey @rohankmr414 , I am using CachyOS with GNOME 49.2 but clipboard is working without any problem. and my friend with your exact setup is using it too.