docs: add required output field and import changes to Prisma 7 upgrade guide (#7349)

Fixes #7340 - The upgrade guide was missing information about:
- The output field being required in the generator block
- How to update imports from @prisma/client to the generated path

Co-authored-by: Arthur Gamby <[email protected]>

Author: ArthurGamby

content/200-orm/800-more/300-upgrade-guides/200-upgrading-versions/400-upgrading-to-prisma-7.mdx

@@ -118,6 +118,7 @@ The older `prisma-client-js` provider will be removed in future releases of Pris
 the new `prisma-client` provider which uses the new Rust-free client. This will give you faster
 queries, smaller bundle size, and require less system resources when deployed to your server.
 
+Additionally, the `output` field is now **required** in the generator block. Prisma Client will no longer be generated in `node_modules` by default. You must specify a custom output path.
 
 #### Before
 ```prisma
@@ -131,9 +132,26 @@ generator client {
 ```prisma
 generator client {
   provider = "prisma-client"
+  output   = "./generated/prisma"
 }
 ```
 
+After running `npx prisma generate`, you'll need to update your imports to use the new generated path:
+
+```ts
+// Before
+import { PrismaClient } from '@prisma/client'
+
+// After
+import { PrismaClient } from './generated/prisma/client'
+```
+
+:::note
+
+The import path depends on where you place your generated client. Adjust the path based on your `output` configuration and the location of the file you're importing from.
+
+:::
+
 Additionally other fields such as `url`, `directUrl`, and `shadowDatabaseUrl` in the `datasource` block are deprecated. You can configure them in the [Prisma Config](/orm/reference/prisma-config-reference).
 
 If you were previously using `directUrl` to run migrations then you need to pass the `directUrl` value in the `url` field of `prisma.config.ts` instead as the connection string defined in `url` is used by Prisma CLI for migrations.