Update LICENSE.txt to include i18n/ under Apache License v2.0 (#15085)

Automatic Merge

LICENSE.txt

@@ -11,7 +11,7 @@ You may be licensed to use source code to create compiled versions not produced
 1. Under the Free Software Foundation’s GNU AGPL v.3.0, subject to the exceptions outlined in this policy; or
 2. Under a commercial license available from Mattermost, Inc. by contacting commercial@mattermost.com
 
-You are licensed to use the source code in Admin Tools and Configuration Files (templates/, config/default.json, model/,
+You are licensed to use the source code in Admin Tools and Configuration Files (templates/, config/default.json, i18n/, model/,
 plugin/ and all subdirectories thereof) under the Apache License v2.0.
 
 We promise that we will not enforce the copyleft provisions in AGPL v3.0 against you if your application (a) does not