fix(deps): update @sanity/client peer dependency to v7

Author: stipsan

packages/preview-kit/package.json

@@ -109,7 +109,7 @@
     "vitest": "^3.1.2"
   },
   "peerDependencies": {
-    "@sanity/client": "^6.29.0 || ^7.0.0",
+    "@sanity/client": "^7.0.0",
     "react": "^18 || ^19"
   },
   "peerDependenciesMeta": {