Remove unused option.

orig-cargo-toml doesn't seem to exist in cargo2android.py, and removing
it has no effect.

Test: Ran cargo2android.py, no change in Android.bp.
Change-Id: I805e7a6af48ed0a5d6ecf3cb5a4d760daeb3f343
diff --git a/cargo2android.json b/cargo2android.json
index 84d8f2d..3ebdf72 100644
--- a/cargo2android.json
+++ b/cargo2android.json
@@ -2,6 +2,5 @@
   "dependencies": true,
   "device": true,
   "run": true,
-  "tests": true,
-  "orig-cargo-toml": true
+  "tests": true
 }