test-import: remove unneeded chmod call

As pointed out by Mads, setting the x bit on dummypatch.py is unneeded, because
it is called with 'python ../dummypatch.py'.

tests/test-import.t

@@ -54,7 +54,6 @@ import exported patch with external patcher
   > print 'patching file a'
   > file('a', 'wb').write('line2\n')
   > EOF
-  $ chmod +x dummypatch.py
   $ hg clone -r0 a b
   adding changesets
   adding manifests