deps: update com.icegreen:greenmail to v2.1.8

Author: renovate[bot]

gradle/libs.versions.toml

@@ -24,7 +24,7 @@ diffUtils = "4.16"
 exposed = "0.61.0"
 flexmark = "0.64.8"
 freemarker = "2.3.34"
-greenmail = "2.1.7"
+greenmail = "2.1.8"
 gson = "2.13.2"
 hikari = "7.0.2"
 hoplite = "2.9.0"