Bump versions.springBootVersion from 2.3.0.RELEASE to 2.3.1.RELEASE

Bumps `versions.springBootVersion` from 2.3.0.RELEASE to 2.3.1.RELEASE.

Updates `spring-boot-dependencies` from 2.3.0.RELEASE to 2.3.1.RELEASE
- [Release notes](https://github.com/spring-projects/spring-boot/releases)
- [Commits](spring-projects/spring-boot@v2.3.0.RELEASE...v2.3.1.RELEASE)

Updates `spring-boot-gradle-plugin` from 2.3.0.RELEASE to 2.3.1.RELEASE
- [Release notes](https://github.com/spring-projects/spring-boot/releases)
- [Commits](spring-projects/spring-boot@v2.3.0.RELEASE...v2.3.1.RELEASE)

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

dependencies.gradle

@@ -14,7 +14,7 @@ versions.aspectJVersion = "1.9.4"
 versions.apacheDsVersion = "2.0.0.AM26"
 versions.bouncyCastleVersion = "1.66"
 versions.hamcrestVersion = "2.2"
-versions.springBootVersion = "2.3.0.RELEASE"
+versions.springBootVersion = "2.3.1.RELEASE"
 versions.springSecurityJwtVersion = "1.1.1.RELEASE"
 versions.springSecurityOAuthVersion = "2.4.0.RELEASE"
 versions.springSecuritySamlVersion = "1.0.10.RELEASE"