Don't run doc-comment-check-docs for update-api

update-api would be fast except that it spends ~4 minutes doing
doc-comment-check-docs.  doc-comment-check-docs isn't really
related to update-api, so lets just remove it.

Fixes: 124386818
Test: m update-api
Change-Id: I0f5311e98063786671c0d8b6a8db52351d9fcfd7