build: Post-release version bump to 2.99.4
build: Post-release version bump to 2.99.4

Better late than never.

akrisiun/gtk-sharp,antoniusriha/gtk-sharp,orion75/gtk-sharp,akrisiun/gtk-sharp,orion75/gtk-sharp,openmedicus/gtk-sharp,antoniusriha/gtk-sharp,openmedicus/gtk-sharp,antoniusriha/gtk-sharp,sillsdev/gtk-sharp,antoniusriha/gtk-sharp,sillsdev/gtk-sharp,akrisiun/gtk-sharp,orion75/gtk-sharp,sillsdev/gtk-sharp,sillsdev/gtk-sharp,openmedicus/gtk-sharp,akrisiun/gtk-sharp,orion75/gtk-sharp,openmedicus/gtk-sharp,antoniusriha/gtk-sharp,orion75/gtk-sharp,sillsdev/gtk-sharp,openmedicus/gtk-sharp,akrisiun/gtk-sharp,openmedicus/gtk-sharp,openmedicus/gtk-sharp