fix: emitDeclarationOnly in tsconfig.types.json (smithy-lang#452)

Author: trivikr

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

@@ -3,7 +3,8 @@
   "compilerOptions": {
     "removeComments": false,
     "declaration": true,
-    "declarationDir": "dist-types"
+    "declarationDir": "dist-types",
+    "emitDeclarationOnly": true
   },
   "exclude": ["test/**/*", "dist-types/**/*"]
 }