[DRE-maint] gitlab-shell is marked for autoremoval from testing

[Debian testing autoremoval watch]

gitlab-shell 13.3.0+debian-1 is marked for autoremoval from testing on 2020-08-17

It (build-)depends on packages with these RC bugs:
959675: libgrpc++1: libgrpc++1: endless looping with default settings
961193: libgrpc++1: libgrpc++1 must be linked with libatomic on armel/mips/mipsel/powerpc
963583: libgrpc++1: libgrpc++1 changes ABI without changing soname