chore: upgrade @fastify/multipart from 8.3.0 to 8.3.1 (#2215)

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-FASTIFYMULTIPART-8660811

Co-authored-by: snyk-bot <[email protected]>

Author: CharlieC3

package-lock.json

@@ -91,7 +91,7 @@
     "@fastify/cors": "9.0.1",
     "@fastify/formbody": "7.4.0",
     "@fastify/http-proxy": "9.5.0",
-    "@fastify/multipart": "8.3.0",
+    "@fastify/multipart": "8.3.1",
     "@fastify/swagger": "8.15.0",
     "@fastify/type-provider-typebox": "4.0.0",
     "@hirosystems/api-toolkit": "1.6.2",