Remove policy MS.SHAREPOINT4.2v1 due to Microsoft update to custom scripting settings

🗣 Description

Microsoft is making updates to the custom scripting configuration options for Sharepoint and OneDrive. The purpose of this PR is to remove the SCB references to these settings and add the policy, date of removal, and rationale to the removedpolicies.md.

This would be useful because as Microsoft rolls out this update, users of ScubaGear will experience errors as a result of the missing setting. This allows the ScubaGear and the SCBs to be update to date with this setting deprecation.

💭 Motivation and context

Closes #1399

🧪 Testing

N/A currently only an SCB update, code change will be in a follow-up issue and PR.

✅ Pre-approval checklist

[x] This PR has an informative and human-readable title.
[x] PR targets the correct parent branch (e.g., main or release-name) for merge.
[x] Changes are limited to a single goal - eschew scope creep!
[x] Changes are sized such that they do not touch excessive number of files.
[x] Related issues these changes resolve are linked preferably via closing keywords.
[x] All relevant type-of-change labels added.
[x] All relevant project fields are set.
[x] All relevant repo and/or project documentation updated to reflect these changes.
[x] All relevant functional tests passed.
[x] All automated checks (e.g., linting, static analysis, unit/smoke tests) passed.

✅ Pre-merge checklist

[ ] PR passed smoke test check.
[ ] Feature branch has been rebased against changes from parent branch, as needed

Use Rebase branch button below or use this reference to rebase from the command line.
[ ] Resolved all merge conflicts on branch
[ ] Notified merge coordinator that PR is ready for merge via comment mention

✅ Post-merge checklist

[ ] Feature branch deleted after merge to clean up repository.
[ ] Verified that all checks pass on parent branch (e.g., main or release-name) after merge.

cisagov / ScubaGear