gnome3.webkitgtk: 2.20.1 -> 2.20.2

Semi-automatic update generated by https://github.com/ryantm/nixpkgs-update tools.

This update was made based on information from https://repology.org/metapackage/webkitgtk/versions.

These checks were done:

- built on NixOS
- ran ‘/nix/store/h4aballc6wsb4kj32kcjcx5x4vbax6fj-webkitgtk-2.20.2/bin/WebKitWebDriver -h’ got 0 exit code
- ran ‘/nix/store/h4aballc6wsb4kj32kcjcx5x4vbax6fj-webkitgtk-2.20.2/bin/WebKitWebDriver --help’ got 0 exit code
- found 2.20.2 with grep in /nix/store/h4aballc6wsb4kj32kcjcx5x4vbax6fj-webkitgtk-2.20.2
- directory tree listing: https://gist.github.com/e3496e2d8a6b933a107141f5caecb92d

(cherry picked from commit 926dc3881e)

Note from @obadz: merged #40315 to staging accidentally but this should go to
master due to CVE hence this cherry-pick.

pkgs/development/libraries/webkitgtk/2.20.nix

@@ -15,7 +15,7 @@ assert stdenv.isDarwin -> !enableGtk2Plugins;
 with stdenv.lib;
 stdenv.mkDerivation rec {
   name = "webkitgtk-${version}";
-  version = "2.20.1";
+  version = "2.20.2";
 
   meta = {
     description = "Web content rendering engine, GTK+ port";
@@ -28,7 +28,7 @@ stdenv.mkDerivation rec {
 
   src = fetchurl {
     url = "http://webkitgtk.org/releases/${name}.tar.xz";
-    sha256 = "0nc9dj05dbk31ciip08b3rdsfja7ckc5mgagrj030fafza2k5r23";
+    sha256 = "1qi6nnj4qidzija1am9xscwjxwfqwhiy7x39ndriqgzh86i97znz";
   };
 
   patches = optionals stdenv.isDarwin [