test_slru: Fix incorrect format placeholders

Before commit a0ed19e0a9 there was a cast around these, but the cast
inadvertently changed the signedness, but that made the format
placeholder correct.  Commit a0ed19e0a9 removed the casts, so now the
format placeholders had the wrong signedness.

src/test/modules/test_slru/test_slru.c

@@ -151,7 +151,7 @@ test_slru_page_sync(PG_FUNCTION_ARGS)
 	ftag.segno = pageno / SLRU_PAGES_PER_SEGMENT;
 	SlruSyncFileTag(TestSlruCtl, &ftag, path);
 
-	elog(NOTICE, "Called SlruSyncFileTag() for segment %" PRId64 " on path %s",
+	elog(NOTICE, "Called SlruSyncFileTag() for segment %" PRIu64 " on path %s",
 		 ftag.segno, path);
 
 	PG_RETURN_VOID();
@@ -166,7 +166,7 @@ test_slru_page_delete(PG_FUNCTION_ARGS)
 	ftag.segno = pageno / SLRU_PAGES_PER_SEGMENT;
 	SlruDeleteSegment(TestSlruCtl, ftag.segno);
 
-	elog(NOTICE, "Called SlruDeleteSegment() for segment %" PRId64,
+	elog(NOTICE, "Called SlruDeleteSegment() for segment %" PRIu64,
 		 ftag.segno);
 
 	PG_RETURN_VOID();