define central with https

uitest/pom.xml

@@ -24,6 +24,10 @@
     <description>Vaadin UI tests</description>
 
     <repositories>
+        <repository>
+            <id>central</id>
+            <url>https://repo.maven.apache.org/maven2/</url>
+        </repository>
         <repository>
             <id>vaadin-addons</id>
             <url>https://maven.vaadin.com/vaadin-addons</url>