Small fixes to scriptPubKey/scriptSig pull

* Small grammar fixes.

* Lower case #term-scriptPubKey as all our other anchor links are
  lower case

* Replace script/scripts with scriptPubKey/scriptPubKeys in
  _autocrossref.yaml. (Fixes `make test` errors from broken
  auto-crossref links.)
Merge pull request #1 from harding/script-terminology-edit

Small fixes to scriptPubKey/scriptSig pull