Bump springBootVersion from 2.5.7 to 2.6.0

Bumps `springBootVersion` from 2.5.7 to 2.6.0.

Updates `spring-boot-gradle-plugin` from 2.5.7 to 2.6.0
- [Release notes](https://github.com/spring-projects/spring-boot/releases)
- [Commits](spring-projects/spring-boot@v2.5.7...v2.6.0)

Updates `spring-boot-dependencies` from 2.5.7 to 2.6.0
- [Release notes](https://github.com/spring-projects/spring-boot/releases)
- [Commits](spring-projects/spring-boot@v2.5.7...v2.6.0)

---
updated-dependencies:
- dependency-name: org.springframework.boot:spring-boot-gradle-plugin
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: org.springframework.boot:spring-boot-dependencies
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

build.gradle

@@ -15,7 +15,7 @@
  */
 
 buildscript {
-    def springBootVersion = '2.5.7'
+    def springBootVersion = '2.6.0'
     def sonarqubeVersion = '3.3'
     def asciidoctorGradleVersion = '1.6.1'
     def artifactoryVersion = '4.24.23'