Bump spring-boot-maven-plugin from 2.6.3 to 2.6.4

Bumps [spring-boot-maven-plugin](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-maven-plugin
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

pom.xml

@@ -74,7 +74,7 @@
     <paho.version>1.2.5</paho.version>
     <maven.compiler.plugin.version>3.10.0</maven.compiler.plugin.version>
     <maven-surefire-plugin.version>2.22.2</maven-surefire-plugin.version>
-    <spring-boot-maven-plugin.version>2.6.3</spring-boot-maven-plugin.version>
+    <spring-boot-maven-plugin.version>2.6.4</spring-boot-maven-plugin.version>
     <checksum.maven.plugin.version>1.11</checksum.maven.plugin.version>
     <maven.gpg.plugin.version>3.0.1</maven.gpg.plugin.version>
     <buildnumber.plugin.version>3.0.0</buildnumber.plugin.version>