fix: pom.xml to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JAVA-ORGSPRINGFRAMEWORK-7687447
- https://snyk.io/vuln/SNYK-JAVA-ORGSPRINGFRAMEWORK-7687446

pom.xml

@@ -19,7 +19,7 @@
     <properties>
         <!--=== GENERAL / DSPACE-API DEPENDENCIES ===-->
         <java.version>11</java.version>
-        <spring.version>5.3.20</spring.version>
+        <spring.version>5.3.38</spring.version>
         <spring-boot.version>2.6.8</spring-boot.version>
         <spring-security.version>5.6.5</spring-security.version> <!-- sync with version used by spring-boot-->
         <hibernate.version>5.6.5.Final</hibernate.version>
@@ -115,7 +115,7 @@
                             </goals>
                             <configuration>
                                 <rules>
-                                    <DependencyConvergence />
+                                    <DependencyConvergence/>
                                 </rules>
                             </configuration>
                         </execution>