Revert "str: tune the pair from string parsing"

This reverts commit bc91e284.

Parser can't parse automata string inputs where a state containing a pair is also a final state.

NFA a b c d

<<(InitialStateLabel), 0> <a, 1> <b, 2> <c, 3> - <<a, 1> <a, 1> - - - <b, 2> - <b, 2> <c, 3> - <c, 3> - - - <d, 4> <<d, 4> - - - -

enabled an automatic merge when the pipeline for d96b0d91 succeeds

merged