Run chrome_sizes on lacros-amd64-generic-chrome on bionic.

Bug: 1208582
Change-Id: Ice9adbc8e797ac68d907550a01a9bb069add24ef
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3178493
Commit-Queue: Ben Pastene <[email protected]>
Commit-Queue: Sven Zheng <[email protected]>
Auto-Submit: Ben Pastene <[email protected]>
Reviewed-by: Sven Zheng <[email protected]>
Cr-Commit-Position: refs/heads/main@{#924370}
diff --git a/testing/buildbot/test_suite_exceptions.pyl b/testing/buildbot/test_suite_exceptions.pyl
index d6695b3..ba30362 100644
--- a/testing/buildbot/test_suite_exceptions.pyl
+++ b/testing/buildbot/test_suite_exceptions.pyl
@@ -1049,7 +1049,7 @@
           'dimension_sets': [
             {
               'cpu': 'x86-64',
-              'os': 'Ubuntu-16.04',
+              'os': 'Ubuntu-18.04',
             },
           ],
         },