test: remove FLAKY designation for test-http2-client-upload-reject

The test hasn't failed in a long time as far as I can tell. The issue
may have been fixed by various event updates/changes to http2 and
related systems.

Author: Trott

test/parallel/parallel.status

@@ -9,8 +9,6 @@ prefix parallel
 test-domain-error-types: PASS,FLAKY
 
 [$system==win32]
-# https://github.com/nodejs/node/issues/20750
-test-http2-client-upload-reject: PASS,FLAKY
 # https://github.com/nodejs/node/issues/30847
 test-http2-compat-client-upload-reject: PASS,FLAKY
 # https://github.com/nodejs/node/issues/30845