[IA] Delete stray page copy already now in platforms

[chalin]

• Another followup to [IA] Link normalization step for platforms #6232
• Deletes stray /docs/kubernetes file (probably a side effect of VS Code saving copies of deleted files if you happen to have an editor open and make a search-and-replace change in it 🤷)
• Here's the diff between that stray copy and the one in the proper place:

  $ diff content/en/docs/{platforms/,}kubernetes/operator/troubleshooting/target-allocator.md
  333c333
  < [`ServiceMonitor`](https://observability.thomasriley.co.uk/prometheus/configuring-prometheus/using-service-monitors/#:~:text=The%20ServiceMonitor%20is%20used%20to,build%20the%20required%20Prometheus%20configuration.)
  ---
  > [`ServiceMonitor`](https://observability.thomasriley.co.uk/prometheus/configuring-prometheus/using-service-monitors/)

• I've cleaned out the URL above with the #:~: fragment

[tiffany76]

RSLGTM.