mesa: 18.2.2 -> 18.2.3

https://lists.freedesktop.org/archives/mesa-dev/2018-October/207343.html

Optimistically drop disk cache patch, changelog mentions related
changes to cache behavior.

Not sure if those changes address our problem
(can we count on build-id?) so someone more familiar with
this should probably take a look before merging :).

pkgs/development/libraries/mesa/default.nix

@@ -67,7 +67,7 @@ let
 in
 
 let
-  version = "18.2.2";
+  version = "18.2.3";
   branch  = head (splitString "." version);
 in
 
@@ -81,7 +81,7 @@ let self = stdenv.mkDerivation {
       "ftp://ftp.freedesktop.org/pub/mesa/older-versions/${branch}.x/${version}/mesa-${version}.tar.xz"
       "https://mesa.freedesktop.org/archive/mesa-${version}.tar.xz"
     ];
-    sha256 = "1i3ky3d210vi3f5hlr9la1kspdyv093npndxsbzdklw95aqq5fn3";
+    sha256 = "0krhfq1wqxa2ydh5xsb3z4wams975rjj5bw1xsqyrg8sgv0q7gz2";
   };
 
   prePatch = "patchShebangs .";