un-nixes ur lix, a little

I didn't really go attack the docs because we need to pull a bunch of
PRs. I went looking for strings in the code that called lix nix.

Change-Id: I2138bb4dd239096bc530946b281db7f875195b39

src/libexpr/print-ambiguous.cc

@@ -93,7 +93,7 @@ void printAmbiguous(
         str << v.fpoint;
         break;
     default:
-        printError("Nix evaluator internal error: printAmbiguous: invalid value type");
+        printError("Lix evaluator internal error: printAmbiguous: invalid value type");
         abort();
     }
 }