Fix graph vertex ordering during topological ordering (#1546)

## Fix graph vertex ordering during topological ordering

Previous implementation returned vertices in reverse order even when
there are no dependencies in the graph. Iterate the vertices in reverse
order so input order can be retained.

## Checklist before requesting a review
- [ ] Add unit tests for this change.
- [ ] Make sure all tests can pass.
- [ ] Update documents if necessary.
- [ ] Lint and apply fixes to your code by running `lintrunner -a`
- [ ] Is this a user-facing change? If yes, give a description of this
change to be included in the release notes.
- [ ] Is this PR including examples changes? If yes, please remember to
update [example
documentation](https://github.com/microsoft/Olive/blob/main/docs/source/examples.md)
in a follow-up PR.

## (Optional) Issue link

olive/strategy/utils.py

@@ -54,7 +54,11 @@ def topological_sort(self):
         visited = set()
         order = []
 
-        for v in self.vertices:
+        # Since the dependee vertex is inserted in front, iterate the vertices in
+        # reverse order to retain the relative order of vertices in the graph.
+        # Without it the graph vertices are reversed even in cases where no
+        # dependency exist.
+        for v in reversed(self.vertices):
             if v not in visited:
                 self._topological_sort_util(v, visited, order)