Bug 1731777 Remove document_sample ETL

[jklukas]

See https://bugzilla.mozilla.org/show_bug.cgi?id=1731777

Checklist for reviewer:

• Commits should reference a bug or github issue, if relevant (if a bug is referenced, the pull request should include the bug number in the title)
• If the PR comes from a fork, trigger integration CI tests by running the Push to upstream workflow and provide the <username>:<branch> of the fork as parameter. The parameter will also show up
  in the logs of the manual-trigger-required-for-fork CI task together with more detailed instructions.
• If adding a new field to a query, ensure that the schema and dependent downstream schemas have been updated

[jklukas]

Ran

bq rm moz-fx-data-shared-prod:monitoring_derived.document_sample_nonprod_v1
bq rm moz-fx-data-shared-prod:monitoring.document_sample_nonprod