fix(deps): Update dependency @sanity/next-loader to v1.2.15 (main) (#2135)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

packages/next-sanity/package.json

@@ -148,7 +148,7 @@
   "dependencies": {
     "@portabletext/react": "^3.2.0",
     "@sanity/client": "^6.25.0",
-    "@sanity/next-loader": "1.2.14",
+    "@sanity/next-loader": "1.2.15",
     "@sanity/preview-kit": "5.1.29",
     "@sanity/preview-url-secret": "2.1.0",
     "@sanity/visual-editing": "2.12.3",