Bump spring-core from 5.3.14 to 5.3.20

Bumps [spring-core](https://github.com/spring-projects/spring-framework) from 5.3.14 to 5.3.20.
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](spring-projects/spring-framework@v5.3.14...v5.3.20)

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

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

Author: dependabot[bot]

pom.xml

@@ -19,7 +19,7 @@
         <junit.version>4.13.1</junit.version>
         <assertj.version>3.15.0</assertj.version>
         <mockito.version>3.3.3</mockito.version>
-        <springframework.version>5.3.14</springframework.version>
+        <springframework.version>5.3.20</springframework.version>
         <joda-time.version>2.10.2</joda-time.version>
         <jackson.version>2.12.1</jackson.version>
     </properties>