Update nginx.nix, update lcov-report location

Author: dmjio

haskell-miso.org/nix/nginx.nix

@@ -41,7 +41,7 @@ with (import ../../default.nix {});
           enableACME = true;
           locations = {
           "/" = {
-            root = "${pkgs.coverage}/lcov-report";
+            root = pkgs.coverage;
            };
          };
        };