Fix odd number of key-value pairs in info log about pvc size difference

[plkokanov]

After #1373, which changed the log severity from Error to Info of the log describing that a PVC cannot be decreased, because it already has a larger size than what is currently configured, the following error can be observed, because the Info() call did not contain an even number of key-value pairs after the main log message:

{"level":"info","ts":"2025-11-25T12:00:46Z","logger":"controller.VLSingle","msg":"cannot decrease PVC=vlsingle-example size from=30Gi to=40Gi","vlsingle":"example","namespace":"default"}
{"level":"dpanic","ts":"2025-11-25T12:01:47Z","logger":"controller.VLSingle","msg":"odd number of arguments passed as key-value pairs for logging","vlsingle":"example","namespace":"default","ignored key":"cannot decrease PVC size, please check VolumeClaimTemplate configuration"}

This PR moves the extra string "please check VolumeClaimTemplate configuration" to the fmt.Srpintf(...) call and removes the unnecessary cannot decrease PVC size text as it would just be duplicated.

[AndrewChubatiuk]

LGTM! could you please also add a changelog entry for this fix?

[plkokanov]

Added the changelog entry. Hopefully, it's the right place and format (this is my first PR here 😊 )