openvdb: remove openexr and ilmbase dependencies

Neither openexr nor ilmbase dependencies were actually being picked up
(checked with nix why-depends).
Instead, openvdb defaults to building its own vendored Half library since 8.1.0:
https://github.com/AcademySoftwareFoundation/openvdb/commit/5c9f0f9685805d883c187d9f04a8e8cff00e90e2

Also, starting from 11.0.0, OpenEXR 2 will no longer be supported.
Someone else can look into fixing this properly to use system libraries.

pkgs/development/libraries/openvdb/default.nix

@@ -1,4 +1,4 @@
-{ lib, stdenv, fetchFromGitHub, cmake, openexr, boost, jemalloc, c-blosc, ilmbase, tbb }:
+{ lib, stdenv, fetchFromGitHub, cmake, boost, jemalloc, c-blosc, tbb, zlib }:
 
 stdenv.mkDerivation rec
 {
@@ -16,7 +16,7 @@ stdenv.mkDerivation rec
 
   nativeBuildInputs = [ cmake ];
 
-  buildInputs = [ openexr boost tbb jemalloc c-blosc ilmbase ];
+  buildInputs = [ boost tbb jemalloc c-blosc zlib ];
 
   cmakeFlags = [ "-DOPENVDB_CORE_STATIC=OFF" ];