Merge branch 'update-manifest-json-starting-url' into 'master'

Change PWA manifest.json to open / instead of explore projects page

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/133539



Merged-by: drew stachon <730684-drew@users.noreply.gitlab.com>
Approved-by: Sam Beckham <sbeckham@gitlab.com>
Approved-by: Austin Regnery <aregnery@gitlab.com>
Approved-by: drew stachon <730684-drew@users.noreply.gitlab.com>
Reviewed-by: Sam Beckham <sbeckham@gitlab.com>
Reviewed-by: Sacha Guyon <sguyon@gitlab.com>
Co-authored-by: Sacha Guyon <sguyon@gitlab.com>