Drop redundant document-map format note from vault_patch description

The "does not show '#' markers directly" clause was explaining how to
read vault_get_document_map's output, but targetScope's description
already covers heading-depth derivation in full — this was a second,
unnecessary restatement. Keep the "call vault_get_document_map first"
pointer since it's still a useful nudge at the point of use.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>