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/channels/wsapi/api.go

@@ -4,8 +4,8 @@
 package wsapi
 
 import (
-	"github.com/mattermost/mattermost-server/server/v8/channels/app"
-	"github.com/mattermost/mattermost-server/server/v8/channels/app/platform"
+	"github.com/mattermost/mattermost/server/v8/channels/app"
+	"github.com/mattermost/mattermost/server/v8/channels/app/platform"
 )
 
 type API struct {

server/channels/wsapi/status.go

@@ -4,8 +4,8 @@
 package wsapi
 
 import (
-	"github.com/mattermost/mattermost-server/server/public/model"
-	"github.com/mattermost/mattermost-server/server/public/shared/mlog"
+	"github.com/mattermost/mattermost/server/public/model"
+	"github.com/mattermost/mattermost/server/public/shared/mlog"
 )
 
 func (api *API) InitStatus() {

server/channels/wsapi/system.go

@@ -4,7 +4,7 @@
 package wsapi
 
 import (
-	"github.com/mattermost/mattermost-server/server/public/model"
+	"github.com/mattermost/mattermost/server/public/model"
 )
 
 func (api *API) InitSystem() {

server/channels/wsapi/user.go

@@ -4,8 +4,8 @@
 package wsapi
 
 import (
-	"github.com/mattermost/mattermost-server/server/public/model"
-	"github.com/mattermost/mattermost-server/server/v8/channels/app/request"
+	"github.com/mattermost/mattermost/server/public/model"
+	"github.com/mattermost/mattermost/server/v8/channels/app/request"
 )
 
 func (api *API) InitUser() {

server/channels/wsapi/websocket_handler.go

@@ -6,11 +6,11 @@ package wsapi
 import (
 	"net/http"
 
-	"github.com/mattermost/mattermost-server/server/public/model"
-	"github.com/mattermost/mattermost-server/server/public/shared/i18n"
-	"github.com/mattermost/mattermost-server/server/public/shared/mlog"
-	"github.com/mattermost/mattermost-server/server/v8/channels/app"
-	"github.com/mattermost/mattermost-server/server/v8/channels/app/platform"
+	"github.com/mattermost/mattermost/server/public/model"
+	"github.com/mattermost/mattermost/server/public/shared/i18n"
+	"github.com/mattermost/mattermost/server/public/shared/mlog"
+	"github.com/mattermost/mattermost/server/v8/channels/app"
+	"github.com/mattermost/mattermost/server/v8/channels/app/platform"
 )
 
 func (api *API) APIWebSocketHandler(wh func(*model.WebSocketRequest) (map[string]any, *model.AppError)) webSocketHandler {