chore(deps): bump org.xhtmlrenderer:flying-saucer-pdf in /backend

---
updated-dependencies:
- dependency-name: org.xhtmlrenderer:flying-saucer-pdf
  dependency-version: 9.13.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

backend/pom.xml

@@ -261,7 +261,7 @@
         <dependency>
             <groupId>org.xhtmlrenderer</groupId>
             <artifactId>flying-saucer-pdf</artifactId>
-            <version>9.1.22</version>
+            <version>9.13.1</version>
         </dependency>
         <dependency>
             <groupId>org.springdoc</groupId>