add v1.18.5 changelog

[nawazkh]

What type of PR is this?
/kind documentation

What this PR does / why we need it:

• Add CAPZ v1.18.5 changeling

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:

TODOs:

• squashed commits
• includes documentation
• adds unit tests
• cherry-pick candidate

Release note:

NONE

[mboersma]

/lgtm
/approve

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: e1a834bf3b2d79fff2ee3960a123dff52a970ab7

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: mboersma

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Needs approval from an approver in each of these files:

• OWNERS [mboersma]

Approvers can indicate their approval by writing /approve in a comment
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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 53.27%. Comparing base (3a9eb5b) to head (0ddbf57).
Report is 6 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5633   +/-   ##
=======================================
  Coverage   53.27%   53.27%           
=======================================
  Files         272      272           
  Lines       29522    29522           
=======================================
+ Hits        15727    15729    +2     
+ Misses      12980    12978    -2     
  Partials      815      815           

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