Bump spring-expression from 4.2.5.RELEASE to 5.2.21.RELEASE in /src/gui

Bumps [spring-expression](https://github.com/spring-projects/spring-framework) from 4.2.5.RELEASE to 5.2.21.RELEASE.
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](spring-projects/spring-framework@v4.2.5.RELEASE...v5.2.21.RELEASE)

---
updated-dependencies:
- dependency-name: org.springframework:spring-expression
  dependency-type: direct:production
...

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

src/gui/pom.xml

@@ -27,7 +27,7 @@
         <gt-version>21.4</gt-version>
         <geogwt-version>0.4-SNAPSHOT</geogwt-version>
 
-        <spring.version>4.2.5.RELEASE</spring.version>
+        <spring.version>5.2.21.RELEASE</spring.version>
         <spring.security.version>4.0.4.RELEASE</spring.security.version>
 
         <commonsFileuploadVersion>1.2.1</commonsFileuploadVersion>