Removing default value for skipUpgrade to fix flux errors

[pokearu]

Description of changes:
Removing defaults for skipUpgrade to handle unpredictable behavior from Flux controller.

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[mitalipaygude]

/lgtm

[pokearu]

/approve

[eks-distro-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: pokearu

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[codecov]

Codecov Report

Merging #5368 (f1702d1) into main (b527067) will increase coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #5368      +/-   ##
==========================================
+ Coverage   72.48%   72.50%   +0.02%     
==========================================
  Files         440      440              
  Lines       36221    36282      +61     
==========================================
+ Hits        26256    26308      +52     
- Misses       8394     8400       +6     
- Partials     1571     1574       +3     

Impacted Files	Coverage Δ
pkg/api/v1alpha1/cluster_types.go	81.96% <ø> (ø)

... and 7 files with indirect coverage changes

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[mitalipaygude]

/cherrypick release-0.15

[eks-distro-pr-bot]

@mitalipaygude: new pull request created: #5374

In response to this:

/cherrypick release-0.15

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