chore: update pnpm to 8.6.9

package.json

@@ -6,7 +6,7 @@
 		"type": "git",
 		"url": "https://github.com/misskey-dev/misskey.git"
 	},
-	"packageManager": "pnpm@8.6.0",
+	"packageManager": "pnpm@8.6.9",
 	"workspaces": [
 		"packages/frontend",
 		"packages/backend",