fix(k8s): fix regression in sync stop logic

A recent change introduced kebab-casing for the sync keys used with
Mutagen, but this wasn't applied in the sync prefix helper. This led to
syncs not being stopped by the `sync stop` command.

core/src/plugins/kubernetes/sync.ts

@@ -804,7 +804,7 @@ export async function getSyncStatus(params: GetSyncStatusParams): Promise<GetSyn
 }
 
 function getSyncKeyPrefix(ctx: PluginContext, action: SupportedRuntimeAction) {
-  return `k8s--${ctx.environmentName}--${ctx.namespace}--${action.name}--`
+  return kebabCase(`k8s--${ctx.environmentName}--${ctx.namespace}--${action.name}--`)
 }
 
 /**