Enable vaadin-prerelease for snapshot (#953)

Co-authored-by: Serhii Kulykov <iamkulykov@gmail.com>

pom.xml

@@ -22,21 +22,14 @@
    <repositories>
         <!-- repositories are configured in parent but still need this
              when parent is a snapshot -->
-        <repository>
-            <id>vaadin-snapshots</id>
-            <url>https://oss.sonatype.org/content/repositories/vaadin-snapshots/</url>
-            <releases>
-                <enabled>false</enabled>
-            </releases>
-        </repository>
         <repository>
             <id>vaadin-prereleases</id>
             <url>https://maven.vaadin.com/vaadin-prereleases</url>
             <releases>
                 <enabled>true</enabled>
             </releases>
             <snapshots>
-                <enabled>false</enabled>
+                <enabled>true</enabled>
             </snapshots>
         </repository>
     </repositories>