Remove deprecated downlevelIteration option (#4216)

Author: RyanCavanaugh

tsconfig.json

@@ -16,7 +16,6 @@
     "strict": true,
     "target": "ES2018",
     "noEmitOnError": true,
-    "downlevelIteration": true,
     "incremental": true
   },
   "include": ["./src/**/*", "env.d.ts", "eslint.config.mjs", "jest.config.js"],