Remove KafkaChannel upgrade hack

[slinkydeveloper]

Signed-off-by: Francesco Guardiani francescoguard@gmail.com

Reverts #5085, which was required in 0.22 release to upgrade kafka channel

[knative-metrics-robot]

The following is the coverage report on the affected files.
Say /test pull-knative-eventing-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/apis/messaging/v1/subscription_defaults.go	66.7%	100.0%	33.3
pkg/apis/messaging/v1/subscription_validation.go	94.6%	94.1%	-0.5

[codecov]

Codecov Report

Merging #5276 (12a0216) into main (97c0d30) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #5276      +/-   ##
==========================================
+ Coverage   83.34%   83.36%   +0.01%     
==========================================
  Files         243      243              
  Lines        6882     6878       -4     
==========================================
- Hits         5736     5734       -2     
+ Misses        797      796       -1     
+ Partials      349      348       -1     

Impacted Files	Coverage Δ
pkg/apis/messaging/v1/subscription_defaults.go	100.00% <100.00%> (+66.66%)	⬆️
pkg/apis/messaging/v1/subscription_validation.go	80.00% <100.00%> (-1.40%)	⬇️

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[matzew]

/lgtm
/approve

[knative-prow-robot]

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