Fix httpcore dependency needed by httpclient

httpcore has removed annotations used by httpclient and therefore
it would fail to execute the annotation processor.

E.g. the high-availability plugin, which uses the httpclient, won't
compile anymore because is failing to find the missing annotation
removed from httpcore from v4.4.5 onwards.

The wrong httpcore dependency was introduced yesterday with the merge
of Change-Id: I1fc91bce.

Change-Id: I2d45001995806074534c11fc5230765e4c99e5a2
diff --git a/WORKSPACE b/WORKSPACE
index 0f2733b..36dc61b 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -817,8 +817,8 @@
 
 maven_jar(
     name = "httpcore",
-    artifact = "org.apache.httpcomponents:httpcore:4.4.12",
-    sha1 = "21ebaf6d532bc350ba95bd81938fa5f0e511c132",
+    artifact = "org.apache.httpcomponents:httpcore:4.4.4",
+    sha1 = "b31526a230871fbe285fbcbe2813f9c0839ae9b0",
 )
 
 # Test-only dependencies below.