Don't use regex for end of block detection in example (#9806)

Co-authored-by: Daniel Cousens <dcousens@users.noreply.github.com>

Author: dcousens

examples/extend-prisma-schema/schema.ts

@@ -14,7 +14,7 @@ export const lists = {
     db: {
       extendPrismaSchema: schema => {
         // add a (poor) example of a multi-column unique constraint
-        return schema.replace(/(model [^}]+)}/g, '$1@@unique([firstName, lastName])\n}')
+        return schema.slice(0, -1) + '@@unique([firstName, lastName])\n}'
       },
     },
   }),