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

Author: legendecas

test/sequential/sequential.status

@@ -32,6 +32,8 @@ test-tls-psk-client: PASS, FLAKY
 test-tls-securepair-client: PASS, FLAKY
 
 [$arch==arm]
+# https://github.com/nodejs/node/issues/43638
+test-gc-http-client-timeout: PASS,FLAKY
 
 [$arch==s390x]
 # https://github.com/nodejs/node/issues/41286