mullvad-browser: 15.0.2 -> 15.0.3

Release announcement: https://github.com/mullvad/mullvad-browser/releases/tag/15.0.3
Corresponding Firefox ESR: https://www.firefox.com/en-US/firefox/140.6.0/releasenotes/
Fixed Firefox security vulnerabilites: https://www.mozilla.org/en-US/security/advisories/mfsa2025-94/

pkgs/by-name/mu/mullvad-browser/package.nix

@@ -97,7 +97,7 @@ let
     ++ lib.optionals mediaSupport [ ffmpeg ]
   );
 
-  version = "15.0.2";
+  version = "15.0.3";
 
   sources = {
     x86_64-linux = fetchurl {
@@ -109,7 +109,7 @@ let
         "https://tor.eff.org/dist/mullvadbrowser/${version}/mullvad-browser-linux-x86_64-${version}.tar.xz"
         "https://tor.calyxinstitute.org/dist/mullvadbrowser/${version}/mullvad-browser-linux-x86_64-${version}.tar.xz"
       ];
-      hash = "sha256-/bA3oVGVqrADLWPegdMCKsePczEqEHNLrFtJ242o1rI=";
+      hash = "sha256-qrjKGaS4GYp8C4LzElbN9/+v5MYKsVRHaZDsBZe2Bcs=";
     };
   };