Update git git_tag to be 4.2.0 rather than "release".

That ensures that this version will continue to build ParaView 4.2.0 and
not the latest release.

Change-Id: Ic29b8ae72f3b6191d84f022b6766311201afac0f

versions.cmake

@@ -141,7 +141,7 @@ if (ParaView_FROM_GIT)
   # Download PV from GIT
   add_revision(paraview
     GIT_REPOSITORY git://paraview.org/ParaView.git
-    GIT_TAG "release")
+    GIT_TAG "v4.2.0")
 else()
   # Variables to hold the URL and MD5 (optional)
   set (ParaView_URL "http://www.paraview.org/files/v4.2/ParaView-v4.2.0-source.tar.gz" CACHE