Bump spring-core from 5.3.18 to 5.3.20

Bumps [spring-core](https://github.com/spring-projects/spring-framework) from 5.3.18 to 5.3.20.
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](spring-projects/spring-framework@v5.3.18...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

@@ -9,7 +9,7 @@
   <url>http://maven.apache.org</url>
 
   <properties>
-    <spring.version>5.3.18</spring.version>
+    <spring.version>5.3.20</spring.version>
   </properties>
 
   <dependencyManagement>