Fixes shellcheck warning reported in #21496 (comment)

Problem

The error() function in lib.sh already calls exit 1, so the exit 1 on line 17 of check_pg_schema.sh was unreachable:

In ./scripts/check_pg_schema.sh line 17:
	exit 1
        ^----^ SC2317 (info): Command appears to be unreachable.

Solution

Remove the redundant exit 1 since error() already handles exiting.