Bump spring-boot.version from 2.6.4 to 2.6.6

Bumps `spring-boot.version` from 2.6.4 to 2.6.6.

Updates `spring-boot-starter-test` from 2.6.4 to 2.6.6
- [Release notes](https://github.com/spring-projects/spring-boot/releases)
- [Commits](spring-projects/spring-boot@v2.6.4...v2.6.6)

Updates `spring-boot-starter-web` from 2.6.4 to 2.6.6
- [Release notes](https://github.com/spring-projects/spring-boot/releases)
- [Commits](spring-projects/spring-boot@v2.6.4...v2.6.6)

Updates `spring-boot-maven-plugin` from 2.6.4 to 2.6.6
- [Release notes](https://github.com/spring-projects/spring-boot/releases)
- [Commits](spring-projects/spring-boot@v2.6.4...v2.6.6)

---
updated-dependencies:
- dependency-name: org.springframework.boot:spring-boot-starter-test
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.springframework.boot:spring-boot-starter-web
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.springframework.boot:spring-boot-maven-plugin
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

pom.xml

@@ -108,7 +108,7 @@
     <jib-maven-plugin.version>3.2.1</jib-maven-plugin.version>
 
     <!-- Spring -->
-    <spring-boot.version>2.6.4</spring-boot.version>
+    <spring-boot.version>2.6.6</spring-boot.version>
     <spring-data.version>2.5.6</spring-data.version>
 
     <!-- Security -->