Ensure nilaway only scans gitlab-shell

Overview

It turns our we've been running nilaway incorrectly the whole time by not including the -include-pkgs="<YOUR_PKG_PREFIX>,<YOUR_PKG_PREFIX_2>" option. This results in all modules being scanned and can either time out, or consume all memory.

This MR updates the nilaway call to run with -include-pkgs="gitlab.com/gitlab-org/gitlab-shell/v14" which should limit the processing to just gitlab-shell 🤞

https://gitlab.com/gitlab-org/gitlab-shell/-/jobs/9952951183 (from Go 1.24.2 update (!1275 - merged)) is an example of nilaway running with these changes, which produces results and runs in a timely manner.

We're still always returning true (we append || true to the nilaway command) which we should probably remove in place of allowing the CI job to fail and produce a warning instead. Updated with 5b4fee9a 🙂