Mark tcp_socket test flaky (for real)

The tag on the binary has no effect. It must be on the test.

PiperOrigin-RevId: 254103480

test/syscalls/BUILD

@@ -609,6 +609,8 @@ syscall_test(test = "//test/syscalls/linux:sysret_test")
 syscall_test(
     size = "medium",
     shard_count = 10,
+    # FIXME(b/135470853)
+    tags = ["flaky"],
     test = "//test/syscalls/linux:tcp_socket_test",
 )
 

test/syscalls/linux/BUILD

@@ -2939,8 +2939,6 @@ cc_binary(
     testonly = 1,
     srcs = ["tcp_socket.cc"],
     linkstatic = 1,
-    # FIXME(b/135470853)
-    tags = ["flaky"],
     deps = [
         ":socket_test_util",
         "//test/util:file_descriptor",