Do not update project stats for incremental repack
The repository size calculation is changing in Gitaly and will be more expensive to compute. Recomputing the size on an incremental repack is not necessary, so we can save some system resources by not computing it.
details are in #357680 (closed) for the performance characteristics of RepositorySize
with the new way we are computing the size.
Change the code so that we don't recalculate the size when a :incremental_repack
is being done. Keep everything else the same.
Changelog: changed