Bump nimbus-jose-jwt from 6.2 to 7.9 in /dspace-server-webapp

Bumps [nimbus-jose-jwt](https://bitbucket.org/connect2id/nimbus-jose-jwt) from 6.2 to 7.9.
- [Changelog](https://bitbucket.org/connect2id/nimbus-jose-jwt/src/master/CHANGELOG.txt)
- [Commits](https://bitbucket.org/connect2id/nimbus-jose-jwt/branches/compare/7.9..6.2)

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

dspace-server-webapp/pom.xml

@@ -28,7 +28,7 @@
         <!-- Define our starting class for our Spring Boot Application -->
         <start-class>org.dspace.app.rest.Application</start-class>
         <!-- Library for managing JSON Web Tokens (JWT): https://bitbucket.org/connect2id/nimbus-jose-jwt/wiki/Home -->
-        <nimbus-jose-jwt.version>6.2</nimbus-jose-jwt.version>
+        <nimbus-jose-jwt.version>7.9</nimbus-jose-jwt.version>
     </properties>
 
     <profiles>