docs: updates outmoded links

[lukegalbraithrussell]

None of these were 404'ing, as the actual url is not case sensitive and/or we have redirects, but they are noise for our internal check for broken links. Removed some reference sentences as steps from apps api pages do not exist anymore, they redirect to the changelog entry

Category (place an x in each of the [ ])

• bolt (Bolt for Java)
• bolt-{sub modules} (Bolt for Java - optional modules)
• slack-api-client (Slack API Clients)
• slack-api-model (Slack API Data Models)
• slack-api-*-kotlin-extension (Kotlin Extensions for Slack API Clients)
• slack-app-backend (The primitive layer of Bolt for Java)

Requirements

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.97%. Comparing base (7f39adf) to head (299c84a).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1541      +/-   ##
============================================
- Coverage     72.99%   72.97%   -0.03%     
  Complexity     4476     4476              
============================================
  Files           477      477              
  Lines         14223    14223              
  Branches       1483     1483              
============================================
- Hits          10382    10379       -3     
- Misses         2962     2965       +3     
  Partials        879      879              

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