You can use the wbgetentities
method for this. To do this, ask it for the entity that's related to the desired article on enwikivoyage. For example, for an entity where the link exists (Prague):
You get result like this:
<entity id="q1085" type="item" />
If the link doesn't exist (Bronzeville):
The result is:
<entity site="enwikivoyage" title="Bronzeville" missing="" />
(The props=
part of the query is there so that you don't get all the information about the entry, just whether it exists or not.)