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

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

Author: anonrig

test/parallel/parallel.status

@@ -11,6 +11,8 @@ prefix parallel
 test-crypto-keygen: PASS,FLAKY
 # https://github.com/nodejs/node/issues/41201
 test-fs-rmdir-recursive: PASS, FLAKY
+# https://github.com/nodejs/node/issues/49985
+test-runner-watch-mode: PASS, FLAKY
 
 # Windows on ARM
 [$system==win32 && $arch==arm64]