Bump mixin-maven-plugin from 0.1-alpha-39 to 0.1-alpha-40 (#2969)

diff --git a/demo/pom.xml b/demo/pom.xml
index e337487..534bed1 100644
--- a/demo/pom.xml
+++ b/demo/pom.xml
@@ -136,7 +136,7 @@
         <plugin>
           <groupId>com.github.odavid.maven.plugins</groupId>
           <artifactId>mixin-maven-plugin</artifactId>
-          <version>0.1-alpha-39</version>
+          <version>0.1-alpha-40</version>
           <extensions>true</extensions>
         </plugin>
         <plugin>