Enable building 2.18.2 on NixOS 24.05

NixOS 24.05 is now used on the main branch as NixOS#10835 has been merged.

This commit backport the `boehm-gc` fix
(NixOS@b311f51) to the 2.18.2 tag.

flake.nix

@@ -193,14 +193,9 @@
           });
 
         propagatedDeps =
-          [ ((boehmgc.override {
+          [ (boehmgc.override {
               enableLargeConfig = true;
-            }).overrideAttrs(o: {
-              patches = (o.patches or []) ++ [
-                ./boehmgc-coroutine-sp-fallback.diff
-              ];
             })
-            )
             nlohmann_json
           ];
       };