Bump org.simplejavamail:simple-java-mail from 6.7.6 to 8.6.3

Bumps [org.simplejavamail:simple-java-mail](https://github.com/bbottema/simple-java-mail) from 6.7.6 to 8.6.3.
- [Release notes](https://github.com/bbottema/simple-java-mail/releases)
- [Changelog](https://github.com/bbottema/simple-java-mail/blob/master/RELEASE.txt)
- [Commits](bbottema/simple-java-mail@6.7.6...8.6.3)

---
updated-dependencies:
- dependency-name: org.simplejavamail:simple-java-mail
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

xwiki-platform-core/xwiki-platform-notifications/xwiki-platform-notifications-test/xwiki-platform-notifications-test-docker/pom.xml

@@ -128,7 +128,7 @@
     <dependency>
       <groupId>org.simplejavamail</groupId>
       <artifactId>simple-java-mail</artifactId>
-      <version>6.7.6</version>
+      <version>8.6.3</version>
       <scope>test</scope>
     </dependency>
   </dependencies>