Bump spring-expression from 5.0.7.RELEASE to 5.2.21.RELEASE

Bumps [spring-expression](https://github.com/spring-projects/spring-framework) from 5.0.7.RELEASE to 5.2.21.RELEASE.
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](spring-projects/spring-framework@v5.0.7.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>

pom.xml

@@ -74,7 +74,7 @@
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <jdk.version>1.8</jdk.version>
-        <spring.version>5.0.7.RELEASE</spring.version>
+        <spring.version>5.2.21.RELEASE</spring.version>
         <spring-cloud.version>Finchley.RELEASE</spring-cloud.version>
         <dubbo.version>2.6.2</dubbo.version>
         <mongo.driver.version>3.5.0</mongo.driver.version>