Revert "es2019 => es2020"

This reverts commit 0652c8c61cec6cbc1911a2ccbd3b720d85c3769a.

tsconfig.base.json

@@ -1,6 +1,6 @@
 {
   "compilerOptions": {
-    "target": "es2020",
+    "target": "es2019",
     "module": "commonjs",
     "allowJs": true,
     "skipLibCheck": true,