Bump spring.version from 5.3.20 to 5.3.21

Bumps `spring.version` from 5.3.20 to 5.3.21.

Updates `spring-core` from 5.3.20 to 5.3.21
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](https://github.com/spring-projects/spring-framework/compare/v5.3.20...v5.3.21)

Updates `spring-web` from 5.3.20 to 5.3.21
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](https://github.com/spring-projects/spring-framework/compare/v5.3.20...v5.3.21)

Updates `spring-beans` from 5.3.20 to 5.3.21
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](https://github.com/spring-projects/spring-framework/compare/v5.3.20...v5.3.21)

Updates `spring-context` from 5.3.20 to 5.3.21
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](https://github.com/spring-projects/spring-framework/compare/v5.3.20...v5.3.21)

Updates `spring-context-support` from 5.3.20 to 5.3.21
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](https://github.com/spring-projects/spring-framework/compare/v5.3.20...v5.3.21)

Updates `spring-aop` from 5.3.20 to 5.3.21
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](https://github.com/spring-projects/spring-framework/compare/v5.3.20...v5.3.21)

Updates `spring-test` from 5.3.20 to 5.3.21
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](https://github.com/spring-projects/spring-framework/compare/v5.3.20...v5.3.21)

---
updated-dependencies:
- dependency-name: org.springframework:spring-core
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.springframework:spring-web
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.springframework:spring-beans
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.springframework:spring-context
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.springframework:spring-context-support
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.springframework:spring-aop
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.springframework:spring-test
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
diff --git a/pom.xml b/pom.xml
index aecae55..2bbcc97 100644
--- a/pom.xml
+++ b/pom.xml
@@ -65,7 +65,7 @@
 
     <slf4j.version>1.7.32</slf4j.version>
     <log4j.version>2.17.2</log4j.version>
-    <spring.version>5.3.20</spring.version>
+    <spring.version>5.3.21</spring.version>
     <ehcache.version>3.9.9</ehcache.version>
     <io.swagger.version>2.1.10</io.swagger.version>