Remove useless initializations

The struct is already initialized to all zeros right before this, and
randomly initializing a few but not all fields to zero again has no
technical or educational value.

Reviewed-by: Tomasz Rybak <tomasz.rybak@post.pl>
Discussion: https://www.postgresql.org/message-id/flat/a368248e-69e4-40be-9c07-6c3b5880b0a6@eisentraut.org

src/backend/utils/cache/relcache.c

@@ -536,8 +536,6 @@ RelationBuildTupleDesc(Relation relation)
 
 	constr = (TupleConstr *) MemoryContextAllocZero(CacheMemoryContext,
 													sizeof(TupleConstr));
-	constr->has_not_null = false;
-	constr->has_generated_stored = false;
 
 	/*
 	 * Form a scan key that selects only user attributes (attnum > 0).