build: name turbo's tasks the way turbo 2 does

turbo went from 1 to 2 in the version sweep and turbo.json still said
`pipeline`, which turbo 2 refuses before it runs anything: `npm run lint`
and `npm run build` both stopped at "Found `pipeline` field instead of
`tasks`". The key is renamed; nothing under it changes.

Co-authored-by: Hanzo Dev <[email protected]>

turbo.json

@@ -1,6 +1,6 @@
 {
   "$schema": "https://turbo.build/schema.json",
-  "pipeline": {
+  "tasks": {
     "build": {
       "dependsOn": ["prebuild", "^build"],
       "outputs": [".next/**", "!.next/cache/**"]