Bump springVersion from 5.3.9 to 5.3.15

Bumps `springVersion` from 5.3.9 to 5.3.15.

Updates `spring-context-support` from 5.3.9 to 5.3.15
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](https://github.com/spring-projects/spring-framework/compare/v5.3.9...v5.3.15)

Updates `spring-jdbc` from 5.3.9 to 5.3.15
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](https://github.com/spring-projects/spring-framework/compare/v5.3.9...v5.3.15)

Updates `spring-tx` from 5.3.9 to 5.3.15
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](https://github.com/spring-projects/spring-framework/compare/v5.3.9...v5.3.15)

Updates `spring-web` from 5.3.9 to 5.3.15
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](https://github.com/spring-projects/spring-framework/compare/v5.3.9...v5.3.15)

Updates `spring-aop` from 5.3.9 to 5.3.15
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](https://github.com/spring-projects/spring-framework/compare/v5.3.9...v5.3.15)

Updates `spring-test` from 5.3.9 to 5.3.15
- [Release notes](https://github.com/spring-projects/spring-framework/releases)
- [Commits](https://github.com/spring-projects/spring-framework/compare/v5.3.9...v5.3.15)

---
updated-dependencies:
- dependency-name: org.springframework:spring-context-support
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.springframework:spring-jdbc
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.springframework:spring-tx
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.springframework:spring-web
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.springframework:spring-aop
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.springframework:spring-test
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

build.gradle

@@ -14,7 +14,7 @@ ext {
         mybatisVersion = '3.5.9',
         mybatisSpringVersion = '2.0.6',
         mybatisSpringBootStarterVersion = '2.2.1',
-        springVersion = '5.3.9',
+        springVersion = '5.3.15',
         springBootVersion = '2.5.3',
         jsqlparserVersion = '4.3',
         junitVersion = '5.7.2',