Revert "Upgrade auto-value to 1.5.1"

Version 1.5.1 doesn't work with Eclipse Oxygen.1a (4.7.1a) [1].

Revert it until the issue is fixed and a new version is released.

This reverts commit 88ce029e9d9409557f941f157419fd89c39a7ec9.

[1] https://github.com/google/auto/issues/539

Change-Id: I3f864a9795ac296e5489fd7f86bf4db0d1c099c3
diff --git a/WORKSPACE b/WORKSPACE
index 6a9c717..61a59ff 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -420,8 +420,8 @@
 
 maven_jar(
     name = "auto_value",
-    artifact = "com.google.auto.value:auto-value:1.5.1",
-    sha1 = "40f66cc5b4f8078a9cb2f8c1e6ece2e2c10c5021",
+    artifact = "com.google.auto.value:auto-value:1.4.1",
+    sha1 = "8172ebbd7970188aff304c8a420b9f17168f6f48",
 )
 
 maven_jar(