[gnome-builder] Non-fast-forward update to branch bilelmoussaoui/rust-analyzer

[Christian Hergert <chergert src gnome org>]

The branch 'bilelmoussaoui/rust-analyzer' was changed in a way that was not a fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  98a4bbc... r-a: Opt-in for the proc-macro expansion feature

Commits added to the branch:

  f6926b4... rust-analyzer: enable experimental proc-macro