Content-Type fixes in client4.ts and remote_cluster.go (#27887)

Co-authored-by: Mattermost Build <build@mattermost.com>
Co-authored-by: Miguel de la Cruz <miguel@mcrx.me>

server/channels/api4/remote_cluster_test.go

@@ -605,7 +605,7 @@ func TestDeleteRemoteCluster(t *testing.T) {
 		require.Zero(t, initialRC.DeleteAt)
 
 		resp, err := th.SystemAdminClient.DeleteRemoteCluster(context.Background(), rc.RemoteId)
-		CheckNoContentStatus(t, resp)
+		CheckOKStatus(t, resp)
 		require.NoError(t, err)
 
 		deletedRC, appErr := th.App.GetRemoteCluster(rc.RemoteId)