fix(eslint): array type lints (#10139)

### Description

#10128 broke linting. Not sure
why linting didn't run??


https://github.com/vercel/turborepo/blob/main/.github/workflows/lint.yml#L9

### Testing Instructions

Ran locally since lints might not run on CI

Author: chris-olszewski

packages/eslint-config-turbo/src/flat/index.ts

@@ -11,4 +11,4 @@ export default [
       "turbo/no-undeclared-env-vars": "error",
     },
   },
-] satisfies Linter.Config[];
+] satisfies Array<Linter.Config>;