yajl: fix url for fetching archive

Accessing archive using current rev leads to an error saying that:
the given path has multiple possibilities: #Git::Ref:0x00007f4cdbb09cd8, #Git::Ref:0x00007f4cdbb09008

Altering rev variable by adding the extra path resolves the problem

pkgs/development/libraries/yajl/default.nix

@@ -7,7 +7,7 @@ stdenv.mkDerivation rec {
   src = fetchFromGitHub {
     owner = "lloyd";
     repo = "yajl";
-    rev = version;
+    rev = "refs/tags/${version}";
     sha256 = "00yj06drb6izcxfxfqlhimlrb089kka0w0x8k27pyzyiq7qzcvml";
   };