Remove the --max-links GC option

We don't need this anymore now that current filesystems support more
than 32,000 files in a directory.

src/libstore/store-api.cc

@@ -13,7 +13,6 @@ GCOptions::GCOptions()
     action = gcDeleteDead;
     ignoreLiveness = false;
     maxFreed = 0;
-    maxLinks = 0;
 }