Bump spotless-maven-plugin from 1.18.0 to 1.20.0

Bumps [spotless-maven-plugin](https://github.com/diffplug/plugin-maven) from 1.18.0 to 1.20.0.
- [Release notes](https://github.com/diffplug/plugin-maven/releases)
- [Commits](https://github.com/diffplug/plugin-maven/commits)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot-support

pom.xml

@@ -107,7 +107,7 @@
         <sortpom-maven-plugin.version>2.10.0</sortpom-maven-plugin.version>
         <spotbugs-fb-contrib.version>7.4.3.sb</spotbugs-fb-contrib.version>
         <spotbugs-maven-plugin.version>3.1.11</spotbugs-maven-plugin.version>
-        <spotless-maven-plugin.version>1.18.0</spotless-maven-plugin.version>
+        <spotless-maven-plugin.version>1.20.0</spotless-maven-plugin.version>
         <spring.boot.version>2.1.3.RELEASE</spring.boot.version>
         <springfox.version>2.9.2</springfox.version>
         <versions-maven-plugin.version>2.7</versions-maven-plugin.version>