Revert "solvespace: use system mimalloc (#450858)"

This reverts commit 6e123b592e, reversing
changes made to dab90ffd83.

pkgs/by-name/so/solvespace/package.nix

@@ -2,7 +2,6 @@
   lib,
   stdenv,
   fetchFromGitHub,
-  fetchpatch,
   cmake,
   pkg-config,
   wrapGAppsHook3,
@@ -24,7 +23,6 @@
   libspnav,
   libthai,
   libxkbcommon,
-  mimalloc,
   pangomm,
   pcre,
   util-linuxMinimal, # provides libmount
@@ -44,13 +42,6 @@ stdenv.mkDerivation rec {
     fetchSubmodules = true;
   };
 
-  patches = [
-    (fetchpatch {
-      url = "https://gitweb.gentoo.org/repo/gentoo.git/plain/media-gfx/solvespace/files/solvespace-3.1-use-system-mimalloc.patch";
-      hash = "sha256-XEeh6vb4fYsTmAro1ZR/8NyFl+Y+S+m/Lx+tA7o2omM=";
-    })
-  ];
-
   nativeBuildInputs = [
     cmake
     pkg-config
@@ -76,7 +67,6 @@ stdenv.mkDerivation rec {
     libspnav
     libthai
     libxkbcommon
-    mimalloc
     pangomm
     pcre
     util-linuxMinimal