build(deps): bump jsoup from 1.14.2 to 1.15.3 in /backend

Bumps [jsoup](https://github.com/jhy/jsoup) from 1.14.2 to 1.15.3.
- [Release notes](https://github.com/jhy/jsoup/releases)
- [Changelog](https://github.com/jhy/jsoup/blob/master/CHANGES)
- [Commits](https://github.com/jhy/jsoup/compare/jsoup-1.14.2...jsoup-1.15.3)

---
updated-dependencies:
- dependency-name: org.jsoup:jsoup
  dependency-type: direct:production
...

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

backend/pom.xml

@@ -267,7 +267,7 @@
         <dependency>
             <groupId>org.jsoup</groupId>
             <artifactId>jsoup</artifactId>
-            <version>1.14.2</version>
+            <version>1.15.3</version>
         </dependency>
 
         <dependency>