Expand worker pool size

Streaming resources requires a third connection to the DB

merlin-worker/src/main/java/gov/nasa/jpl/aerie/merlin/worker/MerlinWorkerAppDriver.java

@@ -42,7 +42,7 @@ public static void main(String[] args) throws InterruptedException {
     hikariConfig.addDataSourceProperty("applicationName", "Merlin Server");
     hikariConfig.setUsername(postgresStore.user());
     hikariConfig.setPassword(postgresStore.password());
-    hikariConfig.setMaximumPoolSize(2);
+    hikariConfig.setMaximumPoolSize(3);
 
     hikariConfig.setConnectionInitSql("set time zone 'UTC'");