cleanup: remove dead cleanupNodesAfterSelectorChange code path

[dorodb-web22]

Since nodeSelector was made immutable in #164, the cleanupNodesAfterSelectorChange function is no longer reachable during reconciliation. The entire function and its call site in Reconcile can be removed as dead code.

This will improve maintainability by removing unused paths.

Note: Per @ajaysundark ’s suggestion, this supersedes issue #230 and PR #231.

[dorodb-web22]

/ASSIGN