Bump org.springframework:spring-webmvc in /interop-mock

Bumps [org.springframework: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] <[email protected]>

Author: dependabot[bot]

interop-mock/pom.xml

@@ -35,7 +35,7 @@
         <dependency>
             <groupId>org.springframework</groupId>
             <artifactId>spring-webmvc</artifactId>
-            <version>3.1.2.RELEASE</version>
+            <version>5.2.20.RELEASE</version>
         </dependency>
         <dependency>
             <groupId>javax.servlet</groupId>