Removed old comment on cluster creation referring to KRaft migration

[ppatierno]

Trivial PR to remove a comment (on cluster creation) which still refers to old KRaft migration.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.79%. Comparing base (ee5e674) to head (d4af55b).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #11987      +/-   ##
============================================
- Coverage     74.81%   74.79%   -0.02%     
+ Complexity     6412     6408       -4     
============================================
  Files           342      342              
  Lines         24207    24207              
  Branches       3185     3185              
============================================
- Hits          18110    18106       -4     
- Misses         4831     4832       +1     
- Partials       1266     1269       +3     

Files with missing lines	Coverage Δ
...cluster/operator/assembly/KafkaClusterCreator.java	94.73% <ø> (ø)

... and 2 files with indirect coverage changes

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