[ch123129] Fix PollingDataSourceBuilder example. (#299)

Author: gwhelanLD

src/main/java/com/launchdarkly/sdk/server/integrations/PollingDataSourceBuilder.java

@@ -18,7 +18,7 @@
  * change its properties with the methods of this class, and pass it to {@link com.launchdarkly.sdk.server.LDConfig.Builder#dataSource(DataSourceFactory)}:
  * <pre><code>
  * LDConfig config = new LDConfig.Builder()
- * .dataSource(Components.pollingDataSource().pollIntervalMillis(45000))
+ * .dataSource(Components.pollingDataSource().pollInterval(Duration.ofSeconds(45)))
  * .build();
  * </code></pre>
  * <p>