Bump spring-webmvc from 3.1.2.RELEASE to 5.2.20.RELEASE in /demo

Bumps [spring-webmvc](https://github.com/spring-projects/spring-framework) from 3.1.2.RELEASE to 5.2.20.RELEASE.
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](spring-projects/spring-framework@v3.1.2.RELEASE...v5.2.20.RELEASE)

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

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

Author: dependabot[bot]

demo/pom.xml

@@ -88,7 +88,7 @@
         <dependency>
             <groupId>org.springframework</groupId>
             <artifactId>spring-webmvc</artifactId>
-            <version>3.1.2.RELEASE</version>
+            <version>5.2.20.RELEASE</version>
             <type>jar</type>
         </dependency>
         <dependency>