Cleanup: explicitly ignore error when requesting shutdown

Explicitly ignore an error when requesting the Manager to shut down.
This was already ignored implicitly, but now it's explicit to make
linters happy.

No functional changes.

internal/manager/api_impl/api_impl.go

@@ -96,7 +96,7 @@ func (f *Flamenco) requestShutdown() {
 	defer func() {
 		// Recover the panic that happens when the channel is closed multiple times.
 		// Requesting a shutdown should be possible multiple times without panicing.
-		recover()
+		_ = recover()
 	}()
 	close(f.done)
 }