Fix hard-coded relkind constants in assorted src/bin files.

Fix hard-coded relkind constants in assorted src/bin files.

Although it's reasonable to expect that most of these constants will
never change, that does not make it good programming style to hard-code
the value rather than using the RELKIND_FOO macros.

Discussion: https://postgr.es/m/11145.1488931324@sss.pgh.pa.us