pgsql: Fix replication/worker_internal.h to compile without other heade

Fix replication/worker_internal.h to compile without other headers.

This header hasn't changed recently, so the fact that it now fails
headerscheck/cpluspluscheck testing must be due to changes in what
it includes.  Probably f21916791 is to blame, but I didn't try to
verify that.

Discussion: https://postgr.es/m/3699703.1595016554@sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/9b14280b207053f8b09e20b5719785ec4413b9d2

Modified Files
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src/include/replication/worker_internal.h | 2 ++
1 file changed, 2 insertions(+)