Update libs.versions.toml

Author: fdevans

gradle/libs.versions.toml

@@ -5,7 +5,7 @@ eddsa = "0.3.0"
 bouncycastle = "1.79"
 expectit = "0.9.0"
 commonsIo = "2.17.0"
-rundeckCore = "6.0.0-SNAPSHOT"
+rundeckCore = "6.0.0-alpha1-20260407"
 slf4j = "2.0.17"
 junit = "4.13.2"
 groovy = "4.0.29"