fix: accept single prover publisher

Author: alexghr

yarn-project/node-keystore/src/schemas.ts

@@ -61,7 +61,7 @@ const proverKeyStoreSchema = z.union([
   ethAccountSchema,
   z.object({
     id: ethAddressSchema,
-    publisher: z.array(ethAccountsSchema),
+    publisher: ethAccountsSchema,
   }),
 ]);