context: stop catching and re-raising FilteredRepoLookupError

FilteredRepoLookupError is only raised by changectx's constructor and
the higher-level scmutil.revsymbol(), so there's no need to catch it
in changectx's constructor.

Differential Revision: https://phab.mercurial-scm.org/D4806

mercurial/context.py

@@ -445,8 +445,6 b' class changectx(basectx):'
         except (error.FilteredIndexError, error.FilteredLookupError):
             raise error.FilteredRepoLookupError(_("filtered revision '%s'")
                                                 % pycompat.bytestr(changeid))
-        except error.FilteredRepoLookupError:
-            raise
         except IndexError:
             pass
         raise error.RepoLookupError(