test: mark test-http2-session-timeout as flake on ARM

PR-URL: #23639
Refs: #20628
Reviewed-By: Rich Trott <[email protected]>

Author: refack

Diff for: test/sequential/sequential.status

@@ -21,3 +21,7 @@ test-http2-large-file: PASS, FLAKY
 [$system==freebsd]
 
 [$system==aix]
+
+[$arch==arm]
+# https://github.com/nodejs/node/issues/20628
+test-http2-session-timeout: PASS,FLAKY