Removes the OWNERS expansion test from metrics_python_tests.

This test is unnecessary because the bots already fail when there is an
invalid path to an OWNERS file in histograms.xml.

CL with failing bots: crrev.com/c/1745447.

Some existing tests, e.g. generate_expired_histograms_array.py, and the
validate_format.py PRESUBMIT merge the histograms, which also performs
OWNERS expansion. Any OWNERS expansion errors are already caught and
will prevent a CL from being submitted.

Bug: 924136
Change-Id: I9205fe4ce08703ac1f7f10b1c0d0e19eef829361
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1749247
Commit-Queue: Caitlin Fischer <caitlinfischer@google.com>
Commit-Queue: Alexei Svitkine <asvitkine@chromium.org>
Auto-Submit: Caitlin Fischer <caitlinfischer@google.com>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#686034}

tools/metrics/BUILD.gn

@@ -101,7 +101,6 @@ group("metrics_python_tests") {
 
     "//tools/metrics/histograms/enums.xml",
     "//tools/metrics/histograms/expand_owners.py",
-    "//tools/metrics/histograms/expand_owners_in_histograms_xml_unittest.py",
     "//tools/metrics/histograms/expand_owners_unittest.py",
     "//tools/metrics/histograms/extract_histograms.py",
     "//tools/metrics/histograms/generate_expired_histograms_array.py",

tools/metrics/metrics_python_tests.py

@@ -21,7 +21,6 @@ def resolve(*paths):
 
 sys.exit(typ.main(tests=resolve(
    'actions/extract_actions_test.py',
-   'histograms/expand_owners_in_histograms_xml_unittest.py',
    'histograms/generate_expired_histograms_array_unittest.py',
    'histograms/pretty_print_test.py',
    'rappor/rappor_model_test.py',