Mark completion_test as slow in checked mode.

pkg/pkg.status

Index: pkg/pkg.status
diff --git a/pkg/pkg.status b/pkg/pkg.status
index c991ab2608fe621fa2239ec27c9c02f55f07d01f..a78a08d6cccfec5f89818237a2b77245fe9dc6f6 100644
--- a/pkg/pkg.status
+++ b/pkg/pkg.status
@@ -22,6 +22,9 @@ lookup_map/*: SkipByDesign
 [ $runtime == vm && $mode == debug ]
 analysis_server/test/completion_test: Pass, Slow
 
+[ $runtime == vm && $checked ]
+analysis_server/test/completion_test: Pass, Slow
+
 [ $runtime == vm && $system == windows]
 analysis_server/test/analysis/get_errors_test: Skip # runtime error, Issue 22180
 analysis_server/test/integration/analysis/analysis_options_test: RuntimeError # Issue 24796