test: enable sparse-revlog for test-narrow-clone.t

We are about to enable sparse-revlog globally. To help with reviewing the
tests change, we isolate them in individual changesets.

Differential Revision: https://phab.mercurial-scm.org/D5327

tests/test-narrow-clone.t

@@ -1,3 +1,9 b''
+TRANSITIONAL CONFIG
+  $ cat << EOF >> $HGRCPATH
+  > [format]
+  > sparse-revlog = yes
+  > EOF
+
   $ . "$TESTDIR/narrow-library.sh"
 
   $ hg init master
@@ -43,6 +49,7 b' narrow clone a file, f10'
   fncache
   narrowhg-experimental
   revlogv1
+  sparserevlog
   store
   testonly-simplestore (reposimplestore !)