no need in java 8

Differential Revision: https://phabricator.twitter.biz/D1247374

Author: Eugene Slutsky

util-validator/src/main/scala/com/twitter/util/validation/BUILD

@@ -1,7 +1,7 @@
 scala_library(
     sources = ["*.scala"],
     compiler_option_sets = ["fatal_warnings"],
-    platform = "java8-do-not-use",
+    platform = "java8",
     provides = scala_artifact(
         org = "com.twitter",
         name = "util-validation-core",