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](https://github.com/spring-projects/spring-framework/compare/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>
diff --git a/pom.xml b/pom.xml
index 7bfed2c..4fb4b08 100644
--- a/pom.xml
+++ b/pom.xml
@@ -110,7 +110,7 @@
         <bouncycastle.version>1.70</bouncycastle.version>
         <slf4j.version>1.7.32</slf4j.version>
         <logback.version>1.2.9</logback.version>
-        <spring.version>5.3.14</spring.version>
+        <spring.version>5.3.20</spring.version>
             <!-- NOTE: upgrading to 6.x requires Java 11 -->
         <jgit.version>5.13.0.202109080827-r</jgit.version>
         <junit.version>4.13.2</junit.version>