Bump spring-webmvc from 5.2.20.RELEASE to 5.2.21.RELEASE

Bumps [spring-webmvc](https://github.com/spring-projects/spring-framework) from 5.2.20.RELEASE to 5.2.21.RELEASE.
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](spring-projects/spring-framework@v5.2.20.RELEASE...v5.2.21.RELEASE)

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

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

Author: dependabot[bot]

pom.xml

@@ -40,7 +40,7 @@
         <onebusaway.siri.version>1.0.0</onebusaway.siri.version>
         <onebusaway.siri_2.version>1.0.3</onebusaway.siri_2.version>
         <protobuf.version>2.6.1</protobuf.version>
-        <spring.version>5.2.20.RELEASE</spring.version>
+        <spring.version>5.2.21.RELEASE</spring.version>
         <struts.version>2.5.30</struts.version>
         <xwiki.integration.version>1.0.1</xwiki.integration.version>
         <xwiki.version>2.3.1</xwiki.version>