Bump junit in /spring-boot/spring-boot-openapi-impl/specification

Bumps [junit](https://github.com/junit-team/junit4) from 4.8.1 to 4.13.1.
- [Release notes](https://github.com/junit-team/junit4/releases)
- [Changelog](https://github.com/junit-team/junit4/blob/main/doc/ReleaseNotes4.13.1.md)
- [Commits](https://github.com/junit-team/junit4/compare/r4.8.1...r4.13.1)

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

spring-boot/spring-boot-openapi-impl/specification/pom.xml

@@ -16,7 +16,7 @@
         <jackson-version>2.10.2</jackson-version>
         <jodatime-version>2.7</jodatime-version>
         <maven-plugin-version>1.0.0</maven-plugin-version>
-        <junit-version>4.8.1</junit-version>
+        <junit-version>4.13.1</junit-version>
         <springfox-version>2.9.2</springfox-version>
         <threetenbp-version>1.3.8</threetenbp-version>
         <datatype-threetenbp-version>2.6.4</datatype-threetenbp-version>