Bump com.icegreen:greenmail (#203)

Bumps the development-dependencies group with 1 update in the /supplier/spring-mail-supplier directory: [com.icegreen:greenmail](https://github.com/greenmail-mail-test/greenmail).


Updates `com.icegreen: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:production
  update-type: version-update:semver-patch
  dependency-group: development-dependencies
...

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Author: dependabot[bot]

supplier/spring-mail-supplier/build.gradle

@@ -2,5 +2,5 @@ dependencies {
     api 'org.springframework.integration:spring-integration-mail'
     api 'org.springframework.boot:spring-boot-starter-mail'
 
-    testImplementation 'com.icegreen:greenmail:2.1.7'
+    testImplementation 'com.icegreen:greenmail:2.1.8'
 }