For 11 only, put back heap_expand_tuple to GetTupleForTrigger().

This is not necessary anymore after 297d627e, but extensions that have
not been recompiled after the fix will not use the new definition of
heap_getattr(). While recompiling those extensions is obviously the
suggested course, it's cheap enough to retain the expansion in
GetTupleForTrigger().

Per suggestion from Andrew Gierth.

Discussion: 87va1x43ot.fsf@news-spur.riddles.org.uk

src/backend/commands/trigger.c

@@ -3396,7 +3396,15 @@ ltrmark:;
 		LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
 	}
 
-	result = heap_copytuple(&tuple);
+	/*
+	 * While this is not necessary anymore after 297d627e, as a defense
+	 * against C code that has not recompiled for minor releases after the
+	 * fix, continue to expand the tuple.
+	 */
+	if (HeapTupleHeaderGetNatts(tuple.t_data) < relation->rd_att->natts)
+		result = heap_expand_tuple(&tuple, relation->rd_att);
+	else
+		result = heap_copytuple(&tuple);
 	ReleaseBuffer(buffer);
 
 	return result;