Re-add CQ-Verified submit requirement as non-blocking

This adds back the submit requirement CQ-Verified, which was previously
added in
https://boringssl.googlesource.com/All-Projects/+/b1aed5051eb3131944e2235951c3cb68c51c9f2b
and removed in
https://boringssl.googlesource.com/All-Projects/+/b888132dc1dd2ae5694a579f91307f992e18c1a8
however this time, it is a no-op (because it's only applicable under
conditions that are true when it is submittable), and relies only on the
Presubmit-BoringSSL-Verified+1 label, omitting the "will be verified"
condition (which assumes CQ+2 will run).

The purpose is to populate the UI with a handy indicator of whether the
CL has passed a dry run. Under these circumstances, the CL is as safe to
submit manually (even if CQ cannot be run, e.g. due to infra trouble) as
if it were submitted through CQ.

Change-Id: Ie97dc09dc569f9c4b27943c2e4f3c20eec666f35
Reviewed-on: https://boringssl-review.googlesource.com/c/All-Projects/+/102967
Reviewed-by: David Benjamin <davidben@google.com>