Pretty print dwa.xml when git cl format is used

Currently the DWA directory is not covered by the XML parser, even
though it defines a pretty_print.py file. Adding the DWA directory to
the relevant list ensures any changes to dwa.xml are formatted
appropriately.

Bug: 403946430
Change-Id: I0954e10285353908914674a9865f556922d27b54
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/6757032
Commit-Queue: Alex Turner <alexmt@chromium.org>
Reviewed-by: Scott Lee <ddoman@chromium.org>

metrics_xml_format.py

@@ -15,6 +15,7 @@ def GetMetricsDir(top_dir, path):
     top_dir = os.path.realpath(top_dir)
     metrics_xml_dirs = [
         os.path.join(top_dir, 'tools', 'metrics', 'actions'),
+        os.path.join(top_dir, 'tools', 'metrics', 'dwa'),
         os.path.join(top_dir, 'tools', 'metrics', 'histograms'),
         os.path.join(top_dir, 'tools', 'metrics', 'structured'),
         os.path.join(top_dir, 'tools', 'metrics', 'ukm'),