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/go.mod

@@ -1,4 +1,4 @@
-module github.com/mattermost/mattermost-server/server/v8
+module github.com/mattermost/mattermost/server/v8
 
 go 1.19
 
@@ -46,7 +46,7 @@ require (
 	github.com/mattermost/gziphandler v0.0.1
 	github.com/mattermost/ldap v0.0.0-20201202150706-ee0e6284187d
 	github.com/mattermost/logr/v2 v2.0.16
-	github.com/mattermost/mattermost-server/server/public v0.0.0-00010101000000-000000000000
+	github.com/mattermost/mattermost/server/public v0.0.0-00010101000000-000000000000
 	github.com/mattermost/morph v1.0.5-0.20230511171014-e76e25978d56
 	github.com/mattermost/rsc v0.0.0-20160330161541-bbaefb05eaa0
 	github.com/mattermost/squirrel v0.2.0
@@ -255,4 +255,4 @@ exclude (
 	github.com/willf/bitset v1.2.0
 )
 
-replace github.com/mattermost/mattermost-server/server/public => ./public
+replace github.com/mattermost/mattermost/server/public => ./public