build(deps-dev): bump com.icegreen:greenmail from 2.1.7 to 2.1.8

Bumps [com.icegreen:greenmail](https://github.com/greenmail-mail-test/greenmail) from 2.1.7 to 2.1.8.
- [Release notes](https://github.com/greenmail-mail-test/greenmail/releases)
- [Commits](greenmail-mail-test/greenmail@release-2.1.7...release-2.1.8)

---
updated-dependencies:
- dependency-name: com.icegreen:greenmail
  dependency-version: 2.1.8
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

modules/transport/mail/pom.xml

@@ -63,7 +63,7 @@
         <dependency>
             <groupId>com.icegreen</groupId>
             <artifactId>greenmail</artifactId>
-            <version>2.1.7</version>
+            <version>2.1.8</version>
             <scope>test</scope>
         </dependency>
     </dependencies>