MM-53032: Fix module path after repo rename (#23689)

It was a good decision in hindsight to keep the public module as 0.x
because this would have been a breaking change again.

https://mattermost.atlassian.net/browse/MM-53032
```release-note
Changed the Go module path from github.com/mattermost/mattermost-server/server/v8 to github.com/mattermost/mattermost/server/v8.

For the public facing module, it's path is also changed from github.com/mattermost/mattermost-server/server/public to github.com/mattermost/mattermost/server/public
```

server/platform/services/cache/mocks/Provider.go

@@ -5,7 +5,7 @@ package mocks
 import (
 	mock "github.com/stretchr/testify/mock"
 
-	cache "github.com/mattermost/mattermost-server/server/v8/platform/services/cache"
+	cache "github.com/mattermost/mattermost/server/v8/platform/services/cache"
 )
 
 // Provider is an autogenerated mock type for the Provider type