test: set test-runner-watch-mode as flaky

PR-URL: nodejs/node#50221
Refs: nodejs/node#49985
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Robert Nagy <ronagy@icloud.com>

graal-nodejs/test/parallel/parallel.status

@@ -262,6 +262,8 @@ test-fs-rmdir-recursive: PASS, FLAKY
 # https://github.com/nodejs/node/issues/48300
 test-child-process-pipe-dataflow: PASS, FLAKY
 test-child-process-stdio-reuse-readable-stdio: PASS, FLAKY
+# https://github.com/nodejs/node/issues/49985
+test-runner-watch-mode: PASS, FLAKY
 
 # Windows on ARM
 [$system==win32 && $arch==arm64]