Bump com.icegreen:greenmail from 2.1.0-alpha-4 to 2.1.0-rc-1

Bumps [com.icegreen:greenmail](https://github.com/greenmail-mail-test/greenmail) from 2.1.0-alpha-4 to 2.1.0-rc-1.
- [Release notes](https://github.com/greenmail-mail-test/greenmail/releases)
- [Commits](greenmail-mail-test/greenmail@release-2.1.0-alpha-4...release-2.1.0-rc-1)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

dependencies.gradle

@@ -11,7 +11,7 @@ ext {
     ftpserverCore = 'org.apache.ftpserver:ftpserver-core:1.2.0'
     mockserverNetty = 'org.mock-server:mockserver-netty:5.15.0'
     twitter4jStream = 'org.twitter4j:twitter4j-stream:4.0.7'
-    greenmail = 'com.icegreen:greenmail:2.1.0-alpha-4'
+    greenmail = 'com.icegreen:greenmail:2.1.0-rc-1'
     apacheCuratorTest = 'org.apache.curator:curator-test:5.5.0'
     djlSpringAutoconfigure = "ai.djl.spring:djl-spring-boot-starter-autoconfigure:$djlSpringVersion"
 }