test: mark some tests as flaky

Refs: #20750
Refs: #22327
Refs: #22762
Refs: nodejs/reliability#16

PR-URL: #22941
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>

Author: joaocgreis

test/parallel/parallel.status

@@ -9,6 +9,9 @@ prefix parallel
 test-trace-events-fs-sync: PASS,FLAKY
 
 [$system==win32]
+test-http2-pipe: PASS,FLAKY
+test-worker-syntax-error: PASS,FLAKY
+test-worker-syntax-error-file: PASS,FLAKY
 
 [$system==linux]
 

test/sequential/sequential.status

@@ -10,6 +10,7 @@ prefix sequential
 test-fs-readfile-tostring-fail: PASS, FLAKY
 
 [$system==win32]
+test-http2-large-file: PASS, FLAKY
 
 [$system==linux]