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/shared/driver/conn.go

@@ -7,7 +7,7 @@ import (
 	"context"
 	"database/sql/driver"
 
-	"github.com/mattermost/mattermost-server/server/public/plugin"
+	"github.com/mattermost/mattermost/server/public/plugin"
 )
 
 // Conn is a DB driver conn implementation

server/platform/shared/driver/driver.go

@@ -12,7 +12,7 @@ import (
 	"context"
 	"database/sql/driver"
 
-	"github.com/mattermost/mattermost-server/server/public/plugin"
+	"github.com/mattermost/mattermost/server/public/plugin"
 )
 
 var (

server/platform/shared/driver/objects.go

@@ -7,7 +7,7 @@ import (
 	"context"
 	"database/sql/driver"
 
-	"github.com/mattermost/mattermost-server/server/public/plugin"
+	"github.com/mattermost/mattermost/server/public/plugin"
 )
 
 type wrapperTx struct {