Summary:
b9b57c6f791cb9f28d8bec9372e9a433a903980c / D38176 added the `YBIsCoveredByMainTable` method as a check to see whether an index relation has its own table. That change missed adding this check over the usages of `indisprimary` in f0a5db706e85412ec85a83f8286c892094d83688/D36588 and 59b3636f505a7dc75ae91ab76348b20a89528e90/D38354.
Jira: DB-13134

Test Plan:
Jenkins

This change doesn't really fix any known preexisting bug due to the fact that any call on `yblocalann` to delete or insert a tuple is implemented as a no-op in `yblocalann.c`.

Reviewers: kramanathan

Reviewed By: kramanathan

Subscribers: yql

Differential Revision: https://phorge.dev.yugabyte.com/D38572