[build] Remove legacy hermetic_deps on cat.sh

This was fixed in https://fxrev.dev/511078

Change-Id: Ic4a190f328a2d9b23d1af15893b8245dc090261a
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/515201
Fuchsia-Auto-Submit: Jay Zhuang <jayzhuang@google.com>
Reviewed-by: Shai Barack <shayba@google.com>
Commit-Queue: Auto-Submit <auto-submit@fuchsia-infra.iam.gserviceaccount.com>
diff --git a/build/images/BUILD.gn b/build/images/BUILD.gn
index 3c28984..fb5539f 100644
--- a/build/images/BUILD.gn
+++ b/build/images/BUILD.gn
@@ -2596,7 +2596,6 @@
   visibility = [ ":system_snapshot" ]
   testonly = true
 
-  hermetic_deps = false
   script = "//build/cat.sh"
   sources = []
   outputs = [ "$target_out_dir/$target_name" ]