keyboard: Don't use gtk_widget_show_all

It is removed in GTK+ 4
11 jobs for keyboard-no-show-all in 3 minutes and 40 seconds (queued for 3 seconds)
latest
Status Job ID Name Coverage
  Build
passed #114423
build

00:01:43

 
  Test
passed #114425
asan

00:01:56

passed #114424
test

00:00:40

 
  Manual
manual #114430
allowed to fail manual
armv8
manual #114426
allowed to fail manual
flatpak
manual #114429
allowed to fail manual
msan
manual #114431
allowed to fail manual
ppc64le
manual #114427
allowed to fail manual
tsan
manual #114428
allowed to fail manual
ubsan
 
  Review
manual #114432
allowed to fail manual
review
manual #114433
allowed to fail manual
stop_review