docs: fix typos in code comments (#39968)

- `models/asymkey/error.go`: `IsErrGPGKeyIDAlreadyUsed` doc named the
wrong type (`ErrKeyNameAlreadyUsed` → `ErrGPGKeyIDAlreadyUsed`)
- `modules/lfs/http_client.go`: `batchs` → `batches`
- `routers/web/repo/milestone.go`: `edting` → `editing` (x2), `for
change` → `for changing`

Signed-off-by: Léon Avic Simmons <Avicennasis@gmail.com>

modules/lfs/http_client.go

@@ -29,7 +29,7 @@ type HTTPClient struct {
 	transfers map[string]TransferAdapter
 }
 
-// BatchSize returns the preferred size of batchs to process
+// BatchSize returns the preferred size of batches to process
 func (c *HTTPClient) BatchSize() int {
 	return setting.LFSClient.BatchSize
 }