ci: upgrade Vaadin 24 version to 24.0.0.alpha6

Author: javier-godoy

pom.xml

@@ -461,7 +461,7 @@
 			<properties>
 				<maven.compiler.source>17</maven.compiler.source>
 				<maven.compiler.target>17</maven.compiler.target>
-				<vaadin.version>24.0.0.alpha5</vaadin.version>
+				<vaadin.version>24.0.0.alpha6</vaadin.version>
 				<jetty.version>11.0.12</jetty.version>
 			</properties>
 			<repositories>