test-revert-interactive: eliminate bashism in wildcard pattern

The test failed with Debian dash.

tests/test-revert-interactive.t

@@ -18,7 +18,7 b' 10 run the same test than 8 from within '
   > EOF
 
 
-  $ mkdir -p a/{folder1,folder2}
+  $ mkdir -p a/folder1 a/folder2
   $ cd a
   $ hg init
   $ python $TESTDIR/seq.py 1 5 > f ; hg add f ; hg commit -m "adding f"