Bump spring-boot-dependencies from 2.6.3 to 2.6.4 in /examples

Bumps [spring-boot-dependencies](https://github.com/spring-projects/spring-boot) from 2.6.3 to 2.6.4.
- [Release notes](https://github.com/spring-projects/spring-boot/releases)
- [Commits](spring-projects/spring-boot@v2.6.3...v2.6.4)

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

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

examples/javadoc/build.gradle

@@ -2,7 +2,7 @@ apply plugin: "java"
 apply plugin: "io.freefair.javadocs"
 
 dependencies {
-    implementation platform("org.springframework.boot:spring-boot-dependencies:2.6.3")
+    implementation platform("org.springframework.boot:spring-boot-dependencies:2.6.4")
     implementation "org.springframework.boot:spring-boot-starter-data-jpa"
     implementation "org.springframework.boot:spring-boot-starter-web"
 }