build: remove vaadin prereleases repository

Author: javier-godoy

pom.xml

@@ -70,10 +70,6 @@
             <id>Vaadin Directory</id>
             <url>https://maven.vaadin.com/vaadin-addons</url>
         </repository>
-        <repository>
-            <id>Vaadin prereleases</id>
-            <url>https://maven.vaadin.com/vaadin-prereleases</url>
-        </repository>
     </repositories>
 
     <dependencies>