nix-shell: Fixes use with ruby shebangs.

The ported code in 80ebc553eca19dafc64c47420cd49ddd506bc9b7 was incorrectly ported.

```
-            $envCommand = "exec $execArgs $interpreter -e 'load(\"$script\")' -- ${\(join ' ', (map shellEscape, @savedArgs))}";
...
+                    envCommand = (format("exec %1% %2% -e 'load(\"%3%\") -- %4%") % execArgs % interpreter % script % joined.str()).str();
```

The single-quote finishing the small ruby snippet was lost in
translation.

0 files changed, 0 insertions, 0 deletions