Bazel Docs: Enable docs check in pre- and post-submit (attempt #2).

This CL is a repeat of https://github.com/bazelbuild/bazel/commit/1e6dd50b0b9e2d088169533dcc7073b6df5859da, which was rolled back in https://github.com/bazelbuild/bazel/commit/16cd6aa43b6abd8ddb730d0ceb647c4ce32dcb38 and https://github.com/bazelbuild/bazel/commit/c2dbe6e6bb2b94646ca143ac3c029f80ae95ec01 due to breakages caused by external changes in bazel-contrib/bazel-docs.

We're in a better place now since the CI job is 'soft-fail' and the bazel-docs repo has its own presubmit check to avoid breakages (https://buildkite.com/bazel/bazel-books-bazel-docs).

A potential future improvement would be to store "last green" json files from bazel-docs in a GCS bucket and to use them in the bazelbuild pre/post-submit.

Fixes https://github.com/bazelbuild/continuous-integration/issues/2555

PiperOrigin-RevId: 912105024
Change-Id: If0209ac922f02f600a3970fc8a93227d2f7003ae
diff --git a/.bazelci/postsubmit.yml b/.bazelci/postsubmit.yml
index cdee71b..8fe0701 100644
--- a/.bazelci/postsubmit.yml
+++ b/.bazelci/postsubmit.yml
@@ -1,4 +1,5 @@
 ---
+check_docs: 1
 tasks:
   rockylinux8:
     shell_commands:
diff --git a/.bazelci/presubmit.yml b/.bazelci/presubmit.yml
index d1b5991..d47eb4b 100644
--- a/.bazelci/presubmit.yml
+++ b/.bazelci/presubmit.yml
@@ -1,5 +1,5 @@
 ---
-check_docs: 0
+check_docs: 1
 tasks:
   rockylinux8:
     shell_commands: