Update URL not supported for Mozilla hosted addons

[leplatrem]

Linting fails because of:

[task 2022-05-17T14:07:32.610Z] Code                  Message       Description              File          Line   Column
[task 2022-05-17T14:07:32.610Z] MANIFEST_UPDATE_URL   "update_ur…   "applications.gecko.u…   manifest.j…                
[task 2022-05-17T14:07:32.610Z]                       l" is not     pdate_url" or            son                        
[task 2022-05-17T14:07:32.610Z]                       allowed.      "browser_specific_set…                              
[task 2022-05-17T14:07:32.611Z]                                     tings.gecko.update_ur…                              
[task 2022-05-17T14:07:32.611Z]                                     l" are not allowed for                              
[task 2022-05-17T14:07:32.611Z]                                     Mozilla-hosted                                      
[task 2022-05-17T14:07:32.611Z]                                     add-ons. 

[willdurand]

I left a comment about that in #99: #99 (comment)

I don't think you have anything to do at the moment, this extension does not seem to be listed on AMO.