MM-41988 Updated links to legacy domain about.mm.com (#19552)

* Updated links to legacy domain about.mm.com

* Legacy link updates

* Reverting - only need to change en.json

* Reverting - only need to change en.json

* Reverting - only need to change en.json

* Reverting - only need to change en.json

* Reverting - only need to change en.json

* Reverting - only need to change en.json

* Reverting - only need to change en.json

* Reverting - only need to change en.json

* Reverting - only need to change en.json

* Reverting - only need to change en.json

* Reverting - only need to change en.json

* Reverting - only need to change en.json

* Reverting - only need to change en.json

* Reverting - only need to change en.json

* Reverting - only need to change en.json

* Reverting - only need to change en.json

* Reverting - only need to change en.json

* Reverting - only need to change en.json

* Reverting - only need to change en.json

* about.mm.com URL updates

* mattermost.org URL updates

* forum.mm.org URL update

* Update .github/ISSUE_TEMPLATE.md

* Update .github/ISSUE_TEMPLATE.md

* Un-deleted language files

* Update README.md

* Update tests/test-config.json

* fix some test due to url updating (#19787)

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>
Co-authored-by: Harrison Healey <harrisonmhealey@gmail.com>
Co-authored-by: Ibrahim Serdar Acikgoz <serdaracikgoz86@gmail.com>

api4/post_test.go

@@ -338,7 +338,7 @@ func testCreatePostWithOutgoingHook(
 		outGoingHookResponse := &model.OutgoingWebhookResponse{
 			Text:         model.NewString("some test text"),
 			Username:     "TestCommandServer",
-			IconURL:      "https://www.mattermost.org/wp-content/uploads/2016/04/icon.png",
+			IconURL:      "https://mattermost.com/wp-content/uploads/2022/02/icon.png",
 			Type:         "custom_as",
 			ResponseType: respPostType,
 		}