Bump net.sf.saxon:Saxon-HE from 12.8 to 12.9 (#902)

Bumps net.sf.saxon:Saxon-HE from 12.8 to 12.9.

---
updated-dependencies:
- dependency-name: net.sf.saxon:Saxon-HE
  dependency-version: '12.9'
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
diff --git a/build.gradle b/build.gradle
index 1084db3..dad53b5 100644
--- a/build.gradle
+++ b/build.gradle
@@ -120,7 +120,7 @@
         batikVersion = '1.19'
         graphics2dVersion = '3.0.3'
         pdfboxVersion = '3.0.5'
-        saxonVersion = '12.8'
+        saxonVersion = '12.9'
         xmlSecVersion = '3.0.6'
         apiGuardianVersion = '1.1.2'