ci: upgrade Scalpel to 0.3.7

Fixes inflated affectedModules count where parent POM property changes
(e.g. kafka-version) were reported as affecting all ~670 modules.
Also fixes skipTestsForDownstreamModules not taking effect.

See maveniverse/scalpel#39

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: gnodet

.mvn/extensions.xml

@@ -23,6 +23,6 @@
     <extension>
         <groupId>eu.maveniverse.maven.scalpel</groupId>
         <artifactId>extension3</artifactId>
-        <version>0.3.6</version>
+        <version>0.3.7</version>
     </extension>
 </extensions>