Bump up Yorkie to v0.6.28 (#544)

Author: kokodak

frontend/package.json

@@ -82,7 +82,7 @@
 		"refractor": "^4.8.1",
 		"validator": "^13.12.0",
 		"vite-plugin-package-version": "^1.1.0",
-		"@yorkie-js/sdk": "0.6.26"
+		"@yorkie-js/sdk": "0.6.28"
 	},
 	"devDependencies": {
 		"@sentry/vite-plugin": "^2.20.1",