Bump com.io7m.xstructural.version from 1.8.0 to 1.8.1

Bumps `com.io7m.xstructural.version` from 1.8.0 to 1.8.1.

Updates `com.io7m.xstructural:com.io7m.xstructural.cmdline` 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)

Updates `com.io7m.xstructural:com.io7m.xstructural.xml` 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.cmdline
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: com.io7m.xstructural:com.io7m.xstructural.xml
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

pom.xml

@@ -29,7 +29,7 @@
     <io7m.java.targetJavaVersion>21</io7m.java.targetJavaVersion>
 
     <!-- io7m dependencies. -->
-    <com.io7m.xstructural.version>1.8.0</com.io7m.xstructural.version>
+    <com.io7m.xstructural.version>1.8.1</com.io7m.xstructural.version>
 
     <!-- Third-party dependencies. -->
     <junit.version>5.10.2</junit.version>