chore: TestBench 8.3.0.alpha1 (#7408)

Author: mshabarov

pom.xml

@@ -13,7 +13,7 @@
     <url>https://vaadin.com/components</url>
     <properties>
         <flow.version>23.6-SNAPSHOT</flow.version>
-        <testbench.version>8.2.7</testbench.version>
+        <testbench.version>8.3.0.alpha1</testbench.version>
         <maven.compiler.source>11</maven.compiler.source>
         <maven.compiler.target>11</maven.compiler.target>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>