pgsql: Turn off deprecated bison warnings under MSVC

Turn off deprecated bison warnings under MSVC

These are disabled by the configure code, so this is just fixing an
inconsistency in the MSVC code.

Backpatch to all live branches.

Branch
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REL_11_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/e8a6391fc1837416b7251f62485323af01789559

Modified Files
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src/tools/msvc/pgbison.pl | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)