Bump com.icegreen:greenmail from 1.6.5 to 2.1.0

Bumps [com.icegreen:greenmail](https://github.com/greenmail-mail-test/greenmail) from 1.6.5 to 2.1.0.
- [Release notes](https://github.com/greenmail-mail-test/greenmail/releases)
- [Commits](greenmail-mail-test/greenmail@release-1.6.5...release-2.1.0)

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

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

pom.xml

@@ -16,7 +16,7 @@
     <properties>
         <java.version>21</java.version>
         <version.modelmapper>3.0.0</version.modelmapper>
-        <version.greenmail>1.6.5</version.greenmail>
+        <version.greenmail>2.1.0</version.greenmail>
         <version.mailapi>1.4.3</version.mailapi>
         <spring.test.version>5.1.4.RELEASE</spring.test.version>
     </properties>