Bump spring-core

Bumps [spring-core](https://github.com/spring-projects/spring-framework) from 4.1.2.RELEASE to 4.3.21.RELEASE.
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](https://github.com/spring-projects/spring-framework/compare/v4.1.2.RELEASE...v4.3.21.RELEASE)

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

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

compass/public/assets/highcharts/exporting-server/java/highcharts-export/pom.xml

@@ -16,7 +16,7 @@
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 		<maven.compiler.source>1.7</maven.compiler.source>
 		<maven.compiler.target>1.7</maven.compiler.target>
-		<spring.version>4.1.2.RELEASE</spring.version>
+		<spring.version>4.3.21.RELEASE</spring.version>
 		<maven.build.timestamp.format>yyyyMMddHHmmss</maven.build.timestamp.format>
 		<beanstalk.versionLabel>export-${maven.build.timestamp}</beanstalk.versionLabel>
 	</properties>