python3Packages.multidict: nixfmt

I'm sorry. I only remembered during the push.

pkgs/development/python-modules/multidict/default.nix

···
     typing-extensions
   ];
 
-  env = {} // lib.optionalAttrs stdenv.cc.isClang {
-    NIX_CFLAGS_COMPILE = "-Wno-error=unused-command-line-argument";
-  };
+  env =
+    { }
+    // lib.optionalAttrs stdenv.cc.isClang {
+      NIX_CFLAGS_COMPILE = "-Wno-error=unused-command-line-argument";
+    };
 
   nativeCheckInputs = [
     objgraph