Revert "mesa: 21.0.1 -> 21.0.2"

This reverts commit e3bc983.

It caused segmentation faults for at least Sway and XWayland with the
iris driver, see [0]. The cause and impact of this regression is still
unknown but let's revert it until we know more.

[0]: NixOS#118753 (comment)

pkgs/development/libraries/mesa/default.nix

@@ -32,7 +32,7 @@ with lib;
 let
   # Release calendar: https://www.mesa3d.org/release-calendar.html
   # Release frequency: https://www.mesa3d.org/releasing.html#schedule
-  version = "21.0.2";
+  version = "21.0.1";
   branch  = versions.major version;
 
 self = stdenv.mkDerivation {
@@ -46,7 +46,7 @@ self = stdenv.mkDerivation {
       "ftp://ftp.freedesktop.org/pub/mesa/${version}/mesa-${version}.tar.xz"
       "ftp://ftp.freedesktop.org/pub/mesa/older-versions/${branch}.x/${version}/mesa-${version}.tar.xz"
     ];
-    sha256 = "122vvyk6dgvbfl119pysbdyii6f255r0cg7c8gp2sdsanmdxrha6";
+    sha256 = "1fqj2xhhd1ary0pfg31jq6fqcnd6qgyrw1445nmz554k8n2ck7rp";
   };
 
   prePatch = "patchShebangs .";