Bump plexus from 6.1 to 6.4

Bumps [plexus](https://github.com/codehaus-plexus/plexus-pom) from 6.1 to 6.4.
- [Release notes](https://github.com/codehaus-plexus/plexus-pom/releases)
- [Commits](codehaus-plexus/plexus-pom@plexus-6.1...plexus-6.4)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

pom.xml

@@ -6,7 +6,7 @@
   <parent>
     <groupId>org.codehaus.plexus</groupId>
     <artifactId>plexus</artifactId>
-    <version>6.1</version>
+    <version>6.4</version>
   </parent>
 
   <artifactId>plexus-archiver</artifactId>