narrow: remove a repo file-cache invalidation

It's unclear why this was needed. All tests pass without it. I asked
Kyle Lippincott (who added the check) and he also doesn't remember
what it was for.

Differential Revision: https://phab.mercurial-scm.org/D4097

mercurial/narrowspec.py

@@ -113,9 +113,6 b' def load(repo):'
         # Treat "narrowspec does not exist" the same as "narrowspec file exists
         # and is empty".
         if e.errno == errno.ENOENT:
-            # Without this the next call to load will use the cached
-            # non-existence of the file, which can cause some odd issues.
-            repo.invalidate(clearfilecache=True)
             return set(), set()
         raise
     # maybe we should care about the profiles returned too