header-bar: Remove some unused variables

Fix warnings found by clang.

Signed-off-by: Alexander Mikhaylenko <alexm@gnome.org>
11 jobs for wip/exalm/fixes in 36 minutes and 13 seconds (queued for 11 minutes and 37 seconds)
Status Job ID Name Coverage
  Build
passed #257752
librem5
api-visibility

00:03:00

passed #257754
librem5
build-debian-clang

00:05:16

passed #257753
librem5
build-debian-gcc

00:03:30

passed #257755
librem5
build-fedora-gcc

00:04:46

 
  Test+Docs
passed #257756
librem5
build-gtkdoc

00:02:51

passed #257757
librem5
unit-test

00:03:06

43.7%
 
  Package
passed #257758
librem5
package-debian-buster

00:03:52

passed #257759
librem5:arm64
package-debian-buster:arm64

00:06:37

passed #257760
flatpak
package-flatpak

00:04:22

 
  Test Package
passed #257761
librem5
autopkgtest-debian-buster-package

00:03:19

passed #257762
librem5
lintian-debian-buster-package

00:01:10