Optimize query cache invalidation for ALTER ROLE.

Optimize query cache invalidation for ALTER ROLE.

Commit 6b7d585eb1c693e4ffb5b8e6ed9aa0f067fa1b89 invalidates query
cache if any ALTER ROLE/USER statement is used. Actually this is an
overkill. Because following queries do not affect the privilege of the
role.

- ALTER ROLE user WITH [ENCRYPTED] PASSWORD
- ALTER ROLE user WITH CONNECTION LIMIT

So do not invalidate query cache if those commands are used.

Backpatch-through: v4.1
Discussion: https://www.pgpool.net/pipermail/pgpool-hackers/2024-October/004532.html