use checksum for usda-dash src copy

Reviewed-on: http://git.factory.uga.edu/UGA-Innovation-Factory/athenix/pulls/17

inventory.nix

@@ -121,8 +121,8 @@
         };
       };
       "usda-dash" = builtins.fetchGit {
-        url = "https://git.factory.uga.edu/MODEL/usda-dash-config.git";
-        rev = "a52962b08d21a4c0b1f4f07dcb55146f2078a5d8";
+        url = "git@factory.uga.edu:MODEL/usda-dash-config.git";
+        rev = "49cded91cff4a956d4e01ac6b8fe4efa86f82182";
         submodules = true;
       };
     };