Bump org.codehaus.mojo:flatten-maven-plugin from 1.6.0 to 1.8.0 in /api

Bumps [org.codehaus.mojo:flatten-maven-plugin](https://github.com/mojohaus/flatten-maven-plugin) from 1.6.0 to 1.8.0.
- [Release notes](https://github.com/mojohaus/flatten-maven-plugin/releases)
- [Commits](https://github.com/mojohaus/flatten-maven-plugin/compare/1.6.0...1.8.0)

---
updated-dependencies:
- dependency-name: org.codehaus.mojo:flatten-maven-plugin
  dependency-version: 1.8.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

api/pom.xml

diff --git a/api/pom.xml b/api/pom.xml
index 4700a72..bd9fa38 100644
--- a/api/pom.xml
+++ b/api/pom.xml
@@ -164,7 +164,7 @@
                 <plugin>
                     <groupId>org.codehaus.mojo</groupId>
                     <artifactId>flatten-maven-plugin</artifactId>
-                    <version>1.6.0</version>
+                    <version>1.8.0</version>
                 </plugin>
             </plugins>
         </pluginManagement>