Update guide-changes.md (#29968)

Remove or update outdated contents.

### Checklist

- [ ] This PR has adequate test coverage / QA involvement has been duly
considered. ([trigger-ci for additional test/nightly
runs](https://trigger-ci.dev.materialize.com/))
- [ ] This PR has an associated up-to-date [design
doc](https://github.com/MaterializeInc/materialize/blob/main/doc/developer/design/README.md),
is a design doc
([template](https://github.com/MaterializeInc/materialize/blob/main/doc/developer/design/00000000_template.md)),
or is sufficiently small to not require a design.
  <!-- Reference the design in the description. -->
- [ ] If this PR evolves [an existing `$T ⇔ Proto$T`
mapping](https://github.com/MaterializeInc/materialize/blob/main/doc/developer/command-and-response-binary-encoding.md)
(possibly in a backwards-incompatible way), then it is tagged with a
`T-proto` label.
- [ ] If this PR will require changes to cloud orchestration or tests,
there is a companion cloud PR to account for those changes that is
tagged with the release-blocker label
([example](MaterializeInc/cloud#5021)).
<!-- Ask in #team-cloud on Slack if you need help preparing the cloud
PR. -->
- [ ] If this PR includes major [user-facing behavior
changes](https://github.com/MaterializeInc/materialize/blob/main/doc/developer/guide-changes.md#what-changes-require-a-release-note),
I have pinged the relevant PM to schedule a changelog post.

Author: antiguru

doc/developer/guide-changes.md

@@ -487,16 +487,7 @@ In very rare cases, it may be necessary to merge a PR whose tests are failing.
 This situation typically only occurs with chicken-and-egg CI configuration
 issues, where PR builds are broken until a fix can be merged to `main`.
 
-To perform a "god mode" merge, you can temporarily lift the branch restrictions
-on the `main` branch. Navigate to the [branch protection rules for the `main`
-branch][branch-protection] and uncheck the "Include administrators" box. Do
-*not* delete the rules or uncheck any other boxes, as it is much harder to
-reverse those changes.
-
-Your PR will be mergeable after you uncheck the "Include administrators" box,
-though you will have to click through several warning screens. Once the PR is
-merged, be sure to re-enable the "Include administrators" setting to prevent
-accidents.
+Only a few people have sufficient access, inquire in Slack if this situation arises.
 
 ## Reviewing changes
 
@@ -936,19 +927,6 @@ submit a PR to fix it!
 * Accept PRs that improve the overall health of the codebase, even if they
   are not perfect.
 
-## Common Issues
-
-### Stuck CLA check
-
-Taken from the [cla-assistant `README.md`](https://github.com/cla-assistant/cla-assistant/blob/main/COMMON_ISSUES.md#cla-assistant-status-or-comment-not-updated-1).
-
-Sometimes it happens that while you signed the CLA the status doesn't get updated.
-Might be a technical issue or some other problem. Most temporary issues can be solved by manually triggering a new check with navigating to
-```
-https://cla-assistant.io/check/<orgname>/<reponame>?pullRequest=<pr_number>
-```
-replacing `<orgname>`, `<reponame>` and `<pr_number>` with your respective values.
-
 [`29f8f46b9`]: https://github.com/MaterializeInc/materialize/commit/29f8f46b92280071c96b294d414675aa626f9403
 [#3808]: https://github.com/MaterializeInc/materialize/pull/3808
 [#3982]: https://github.com/MaterializeInc/materialize/pull/3982