Fix documentation links hard-coded to capz.k8s.io

[willie-yao]

What type of PR is this?
/kind documentation

What this PR does / why we need it:
This PR fixes some broken link errors that are caused by links hard-coded to capz.k8s.io instead of the local file, which will cause issues if locations or names of files are changed between versions.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:

• cherry-pick candidate

TODOs:

• squashed commits
• includes documentation
• adds unit tests

Release note:

Fix documentation links hard-coded to capz.k8s.io

[willie-yao]

/assign @nojnhuh

[nojnhuh]

/lgtm
/approve

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 60c250b2c1981145a9aaef43d3c57baed8d775ef

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: nojnhuh

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• OWNERS [nojnhuh]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 51.25%. Comparing base (b4b5087) to head (d857e8c).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5123      +/-   ##
==========================================
- Coverage   51.25%   51.25%   -0.01%     
==========================================
  Files         273      273              
  Lines       24651    24651              
==========================================
- Hits        12636    12634       -2     
- Misses      11229    11231       +2     
  Partials      786      786              

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[willie-yao]

/cherry-pick release-1.16

[k8s-infra-cherrypick-robot]

@willie-yao: #5123 failed to apply on top of branch "release-1.16":

Applying: Fix broken links
Using index info to reconstruct a base tree...
M	docs/book/src/roadmap.md
Falling back to patching base and 3-way merge...
Auto-merging docs/book/src/roadmap.md
CONFLICT (content): Merge conflict in docs/book/src/roadmap.md
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
Patch failed at 0001 Fix broken links
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

In response to this:

/cherry-pick release-1.16

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