src/Pure/System/linux.scala

--- a/src/Pure/System/linux.scala	Mon Apr 05 22:45:01 2021 +0200
+++ b/src/Pure/System/linux.scala	Mon Apr 05 22:46:41 2021 +0200
@@ -45,7 +45,6 @@
     override def toString: String = description
 
     def is_ubuntu: Boolean = id == "Ubuntu"
-    def is_ubuntu_18_04: Boolean = is_ubuntu && release == "18.04"
     def is_ubuntu_20_04: Boolean = is_ubuntu && release == "20.04"
   }