cleanup: leverage yield from in more places

Change-Id: I4f9cb27d89241d3738486764817b51981444a903
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/390274
Reviewed-by: Aravind Vasudevan <aravindvasudev@google.com>
Commit-Queue: Mike Frysinger <vapier@google.com>
Tested-by: Mike Frysinger <vapier@google.com>
diff --git a/manifest_xml.py b/manifest_xml.py
index d2217bb..0392517 100644
--- a/manifest_xml.py
+++ b/manifest_xml.py
@@ -857,8 +857,7 @@
         self._Load()
         outer = self._outer_client
         yield outer
-        for tree in outer.all_children:
-            yield tree
+        yield from outer.all_children
 
     @property
     def all_children(self):
@@ -867,8 +866,7 @@
         for child in self._submanifests.values():
             if child.repo_client:
                 yield child.repo_client
-                for tree in child.repo_client.all_children:
-                    yield tree
+                yield from child.repo_client.all_children
 
     @property
     def path_prefix(self):