CH07: Leave future todo about implications of no script in scriptSig

- E.g., the idea that it might have been possible to implement
  script delegation

chapters/authorization-authentication.adoc

@@ -244,6 +244,7 @@ to spend the UTXO. If any result other than "TRUE" remains after
 execution of the combined script, the input is invalid because it has
 failed to satisfy the spending conditions placed on the output.
 
+//SOMEDAY:implications of not being able to use script in scriptSig
 
 [[p2pkh]]
 ==== Pay-to-Public-Key-Hash (P2PKH)