CI: update debian image

The libc++(abi)-dev packages have been removed because one of their
dependencies conflicted with one of the gstreamer dependencies. As a
result, the gstreamer dependency was not installed and pkg-config was
unable to satisfy the requirements for gstreamer. With the conflicting
package now gone, gstreamer is installed properly and the Debian CI job
is now able to build the gstdecode module.

Amends d0c0a3147a.

extras/ci/gitlab-ci.yml

@@ -23,7 +23,7 @@ variables:
     VLC_WIN64_IMAGE: registry.videolan.org/vlc-debian-win64:20221214115142
     VLC_WIN_LLVM_MSVCRT_IMAGE: registry.videolan.org/vlc-debian-llvm-msvcrt:20221214101739
     VLC_WIN_LLVM_UCRT_IMAGE: registry.videolan.org/vlc-debian-llvm-ucrt:20230523085945
-    VLC_DEBIAN_IMAGE: registry.videolan.org/vlc-debian-unstable:20230621085411
+    VLC_DEBIAN_IMAGE: registry.videolan.org/vlc-debian-unstable:20230705133021
     VLC_ANDROID_IMAGE: registry.videolan.org/vlc-debian-android:20230606050714
     VLC_SNAP_IMAGE: registry.videolan.org/vlc-ubuntu-focal:20221023195550
     VLC_RASPBIAN_IMAGE: registry.videolan.org/vlc-ubuntu-raspberry:20221023200157