nss: Drop nss-pem patchset

The patch url went 404 and other distros¹ have discarded it as well in
favor of packaging nss-pem²

[1] https://gitweb.gentoo.org/repo/gentoo.git/commit/dev-libs/nss?id=5eca3e02c87163b3c541cdee893830d201abfb86
[2] https://github.com/kdudka/nss-pem

pkgs/development/libraries/nss/generic.nix

@@ -19,11 +19,6 @@
 }:
 
 let
-  nssPEM = fetchurl {
-    url = "http://dev.gentoo.org/~polynomial-c/mozilla/nss-3.15.4-pem-support-20140109.patch.xz";
-    sha256 = "10ibz6y0hknac15zr6dw4gv9nb5r5z9ym6gq18j3xqx7v7n3vpdw";
-  };
-
   underscoreVersion = lib.replaceStrings [ "." ] [ "_" ] version;
 in
 stdenv.mkDerivation rec {
@@ -45,13 +40,6 @@ stdenv.mkDerivation rec {
   propagatedBuildInputs = [ nspr ];
 
   prePatch = ''
-    # strip the trailing whitespace from the patch line and the renamed CKO_NETSCAPE_ enum to CKO_NSS_
-    xz -d < ${nssPEM} | sed \
-       -e 's/-DIRS = builtins $/-DIRS = . builtins/g' \
-       -e 's/CKO_NETSCAPE_/CKO_NSS_/g' \
-       -e 's/CKT_NETSCAPE_/CKT_NSS_/g' \
-       | patch -p1
-
     patchShebangs nss
 
     for f in nss/coreconf/config.gypi nss/build.sh nss/coreconf/config.gypi; do