Remove GLOBALTABLESPACE_OID assert for locked buffers.

Commit f4ece891fc added the assertion in
an attempt to catch some defects even after VACUUM FULL or REINDEX.
However, IsCatalogTextUniqueIndexOid(tag.relNumber) always returns false
after a relfilenode change, provoking unintended assertion failures.

Reported-by: Adam Guo <adamguo@amazon.com>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Bug: #18912
Discussion: https://postgr.es/m/18912-a41c9bd0e0ad19b1@postgresql.org

src/backend/storage/buffer/bufmgr.c

@@ -4161,8 +4161,6 @@ AssertNotCatalogBufferLock(LWLock *lock, LWLockMode mode,
 		return;
 
 	Assert(!IsCatalogRelationOid(relid));
-	/* Shared rels are always catalogs: detect even after VACUUM FULL. */
-	Assert(tag.spcOid != GLOBALTABLESPACE_OID);
 }
 #endif