wavegain: Use fetchFromGitHub instead of fetchgit.

pkgs/applications/audio/wavegain/default.nix

···
-{ stdenv, fetchgit }:
+{ stdenv, fetchFromGitHub }:
 
 stdenv.mkDerivation {
   name = "wavegain-1.3.1";
-  src = fetchgit {
-    url = "https://github.com/MestreLion/wavegain.git";
-    sha256 = "1h886xijc9d7h4p6qx12c6kgwmp6s1bdycnyylkayfncczzlbi24";
+  src = fetchFromGitHub {
+    owner = "MestreLion";
+    repo = "wavegain";
+    rev = "c928eaf97aeec5732625491b64c882e08e314fee";
+    sha256 = "0wghqnsbypmr4xcrhb568bfjdnxzzp8qgnws3jslzmzf34dpk5ls";
   };
 
   installPhase = ''