fix: use TS 3.4 compatible types for TS 3.9 (#269)

Author: trivikr

smithy-typescript-codegen/src/main/resources/software/amazon/smithy/typescript/codegen/base-package.json

@@ -40,7 +40,7 @@
     "node": ">=10.0.0"
   },
   "typesVersions": {
-    "<3.9": {
+    "<4.0": {
       "types/*": ["types/ts3.4/*"]
     }
   }