fix: don't ignore not found error in its controller

[cjc7373]

When kb enables IN_PLACE_POD_VERTICAL_SCALING feature gate, but k8s does not, a vscale operation may fail in its because kube-apiserver does not have the "resize" subresource. ITS controller should error emit a warning event like:

Warning  FailedReconcile              15m (x12 over 15m)  instance-set-controller  reconcile failed: the server could not find the requested resource

But instead, its controller silently ignores this error and makes the reconcilation successful.

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[codecov[bot]]

Codecov Report

:x: Patch coverage is 0% with 12 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 50.74%. Comparing base (0b9a9e2) to head (7cc2685). :warning: Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/controller/kubebuilderx/plan_builder.go	0.00%	8 Missing and 3 partials :warning:
pkg/controller/kubebuilderx/controller.go	0.00%	1 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9823      +/-   ##
==========================================
- Coverage   50.86%   50.74%   -0.13%     
==========================================
  Files         542      542              
  Lines       58771    58770       -1     
==========================================
- Hits        29895    29823      -72     
- Misses      25927    25997      +70     
- Partials     2949     2950       +1     

Flag	Coverage Δ
unittests	50.74% <0.00%> (-0.13%)	:arrow_down:

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[cjc7373]

The review comments above are addressed. @leon-inf PTAL