Fix typo in visits form which caused button to miss its text

Signed-off-by: Denis Fuenzalida <denis.fuenzalida@gmail.com>

src/main/resources/templates/pets/createOrUpdateVisitForm.html

@@ -36,7 +36,7 @@
     <div class="form-group">
       <div class="col-sm-offset-2 col-sm-10">
         <input type="hidden" name="petId" th:value="${pet.id}" />
-        <button class="btn btn-primary" type="submit" th:text="${addVisit}">Add Visit</button>
+        <button class="btn btn-primary" type="submit" th:text="#{addVisit}">Add Visit</button>
       </div>
     </div>
   </form>