Bump tsconfig.es.json target to ES2020 (smithy-lang#603)

Author: trivikr

smithy-typescript-codegen/src/main/resources/software/amazon/smithy/typescript/codegen/tsconfig.es.json

@@ -1,17 +1,10 @@
 {
   "extends": "./tsconfig",
   "compilerOptions": {
-    "target": "es5",
+    "target": "ES2020",
     "module": "esnext",
     "moduleResolution": "node",
-    "lib": [
-      "dom",
-      "es5",
-      "es2015.promise",
-      "es2015.collection",
-      "es2015.iterable",
-      "es2015.symbol.wellknown"
-    ],
+    "lib": ["dom"],
     "outDir": "dist-es"
   }
 }