pgsql: Fix compiler warning on MSVC

Fix compiler warning on MSVC

MSVC does not understand that ereport(ERROR) does not return, so just
return the first enum PartitionStrategy value to keep the compiler from
complaining about the missing return.

Discussion: https://postgr.es/m/20221104161934.GB16921@telsasoft.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/1613de8bc34b4977d0186b56ef5a00ef8058a74a

Modified Files
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src/backend/parser/gram.y | 3 +++
1 file changed, 3 insertions(+)