Bump com.io7m.xstructural:com.io7m.xstructural.maven_plugin

Bumps [com.io7m.xstructural:com.io7m.xstructural.maven_plugin](https://github.com/io7m-com/xstructural) from 1.8.0 to 1.8.1.
- [Changelog](https://github.com/io7m-com/xstructural/blob/develop/README-CHANGES.xml)
- [Commits](io7m-com/xstructural@com.io7m.xstructural-1.8.0...com.io7m.xstructural-1.8.1)

---
updated-dependencies:
- dependency-name: com.io7m.xstructural:com.io7m.xstructural.maven_plugin
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

pom.xml

@@ -34,7 +34,7 @@
 
   <properties>
     <com.io7m.quarrel.version>1.6.0</com.io7m.quarrel.version>
-    <com.io7m.xstructural.version>1.8.0</com.io7m.xstructural.version>
+    <com.io7m.xstructural.version>1.8.1</com.io7m.xstructural.version>
     <io7m.api.previousVersion>1.1.0</io7m.api.previousVersion>
     <io7m.java.targetJavaVersion>21</io7m.java.targetJavaVersion>
     <jackson.version>2.17.1</jackson.version>