pgsql: Improve wording for privilege description on certain failure

Log Message:
-----------
Improve wording for privilege description on certain failure messages; the
original misleadingly suggests that only access is meant, causing confusion.
Per recent trouble report by Robert McGehee on pgsql-admin.

Modified Files:
--------------
    pgsql/src/backend/catalog:
        pg_shdepend.c (r1.44 -> r1.45)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/pg_shdepend.c?r1=1.44&r2=1.45)
    pgsql/src/test/regress/expected:
        dependency.out (r1.10 -> r1.11)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/dependency.out?r1=1.10&r2=1.11)
        foreign_data.out (r1.12 -> r1.13)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/foreign_data.out?r1=1.12&r2=1.13)