[fix][test][branch-4.2] Fix ManagedCursorTest compilation

[void-ptr974]

Motivation

The branch-4.2 cherry-pick of #26184 added tests that stub ManagedLedgerImpl#getLogger(). That accessor is only available after the managed-ledger slog migration and is not present in branch-4.2, so managed-ledger test compilation fails.

Modifications

Remove the unnecessary logger stubs from the affected ManagedCursorTest cases.

Verifying this change

This change is already covered by existing tests:

• mvn -pl managed-ledger -Dspotbugs.skip=true "-Dtest=ManagedCursorTest#testEstimatedUnackedSizeWhenLatestLedgerIsEmpty+testEstimatedUnackedSizeWhenCursorCaughtUpWithLastPosition+testEstimatedUnackedSizeWhenCursorAdvancedToEmptyCurrentLedger+testEstimatedUnackedSizeWhenLastPositionLedgerIsNoLongerInLedgerList+testEstimatedUnackedSizeFailsWhenCursorIsUnexpectedlyAheadOfLastPosition" test
• mvn -pl managed-ledger -am -DskipTests -Dspotbugs.skip=true install

Does this pull request potentially affect one of the following parts:

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment