tests: order the imports in test-fastannotate-hg.t

The wrong ordering breaks test-check-module-imports.t on Python 3. I am not sure
why that test is so much active on py3.

Differential Revision: https://phab.mercurial-scm.org/D4496

tests/test-fastannotate-hg.t

@@ -439,7 +439,7 b' and (2) the extension to allow filelog m'
 and its ancestor by overriding "repo._filecommit".
 
   $ cat > ../legacyrepo.py <<EOF
-  > from mercurial import node, error
+  > from mercurial import error, node
   > def reposetup(ui, repo):
   >     class legacyrepo(repo.__class__):
   >         def _filecommit(self, fctx, manifest1, manifest2,