test: mark test-gc-http-client-timeout as flaky on arm

Author: legendecas

test/sequential/sequential.status

@@ -29,9 +29,11 @@ test-buffer-creation-regression: SKIP
 test-perf-hooks: SKIP
 # https://github.com/nodejs/node/issues/39683
 test-tls-psk-client: PASS, FLAKY
+# https://github.com/nodejs/node/issues/43638
 test-tls-securepair-client: PASS, FLAKY
 
 [$arch==arm]
+test-gc-http-client-timeout: PASS,FLAKY
 
 [$arch==s390x]
 # https://github.com/nodejs/node/issues/41286