Improve docs page for updating vSphere creds

[csplinter]

Issue #, if available:
This is a follow-up to this PR #9189

Description of changes:

1. Make Update vSphere credentials its own separate page
2. Recommend using the script
3. Provide only one set of manual steps instead of two

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.45%. Comparing base (383908d) to head (c8b6460).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9365      +/-   ##
==========================================
- Coverage   69.45%   69.45%   -0.01%     
==========================================
  Files         672      672              
  Lines       49357    49357              
==========================================
- Hits        34283    34280       -3     
- Misses      13288    13290       +2     
- Partials     1786     1787       +1     

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