Add chrome-cherry-picker to known robots list.

Add the chrome-cherry-picker service account email to KNOWN_ROBOTS so
the presubmits don't think that this is an external account trying to
commit to src.
Security review bug: https://b.corp.google.com/issues/403244734

Change-Id: I8dad3157cc944a056433f12460afbecbdcb10757
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6425146
Reviewed-by: Daniel Yip <danielyip@google.com>
Commit-Queue: Gennady Tsitovich <gtsitovich@google.com>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1441793}

PRESUBMIT.py

@@ -2470,7 +2470,7 @@ _KNOWN_ROBOTS = set(
                     'skylab-test-cros-roller', 'infra-try-recipes-tester',
                     'chrome-automated-expectation',
                     'chromium-automated-expectation', 'chrome-branch-day',
-                    'chromium-autosharder')
+                    'chrome-cherry-picker', 'chromium-autosharder')
   ) | set('%s@skia-public.iam.gserviceaccount.com' % s
           for s in ('chromium-autoroll', 'chromium-release-autoroll')
   ) | set('%s@skia-corp.google.com.iam.gserviceaccount.com' % s