fix TypeScript test code

Author: eli-darkly

test-types.ts

@@ -2,7 +2,7 @@
 // This file exists only so that we can run the TypeScript compiler in the CI build
 // to validate our index.d.ts file.
 
-import DynamoDBFeatureStore, { LDDynamoDBOptions } from 'launchdarkly-node-server-sdk-dynamodb';
+import { DynamoDBFeatureStore, LDDynamoDBOptions } from 'launchdarkly-node-server-sdk-dynamodb';
 import { LDLogger } from 'launchdarkly-node-server-sdk';
 import { DynamoDB } from 'aws-sdk';