pom.xml: update Spring

We need to keep Spring Framework, Spring Boot, and Spring Security
versions updated together:

- Spring Framework: 5.3.28→5.3.31
- Spring Boot: 2.7.13→2.7.18
- Spring Security: 5.7.9→5.7.11

pom.xml

@@ -19,9 +19,9 @@
     <properties>
         <!--=== GENERAL / DSPACE-API DEPENDENCIES ===-->
         <java.version>11</java.version>
-        <spring.version>5.3.28</spring.version>
-        <spring-boot.version>2.7.13</spring-boot.version>
-        <spring-security.version>5.7.9</spring-security.version> <!-- sync with version used by spring-boot-->
+        <spring.version>5.3.31</spring.version>
+        <spring-boot.version>2.7.18</spring-boot.version>
+        <spring-security.version>5.7.11</spring-security.version> <!-- sync with version used by spring-boot-->
         <hibernate.version>5.6.15.Final</hibernate.version>
         <hibernate-validator.version>6.2.5.Final</hibernate-validator.version>
         <postgresql.driver.version>42.6.0</postgresql.driver.version>