perf: quiet stderr output in perf::unbundle

There a lot of repetitive transaction message we do not care about.

contrib/perf.py

@@ -2668,9 +2668,13 b' def perf_unbundle(ui, repo, fname, **opt'
 
     with repo.lock():
         bundle = [None, None]
+        orig_quiet = repo.ui.quiet
         try:
             with open(fname, mode="rb") as f:
 
+                def noop_report(*args, **kwargs):
+                    pass
+
                 def setup():
                     gen, tr = bundle
                     if tr is not None:
@@ -2679,6 +2683,7 b' def perf_unbundle(ui, repo, fname, **opt'
                     f.seek(0)
                     bundle[0] = exchange.readbundle(ui, f, fname)
                     bundle[1] = repo.transaction(b'perf::unbundle')
+                    bundle[1]._report = noop_report  # silence the transaction
 
                 def apply():
                     gen, tr = bundle

tests/test-contrib-perf.t

@@ -398,8 +398,6 b' Test pre-run feature'
   adding changesets
   adding manifests
   adding file changes
-  transaction abort!
-  rollback completed
 
 
 test  profile-benchmark option