double shad dependency issue in other dependencies grammar

[heacu]

@FChrispz as per the conclusion of tibetan-nlp/classical-tibetan-corpus#1, following advice from @ngawangtrinley, in a sequence of multiple shad, each shad should be made to depend on the preceding verb. You can see examples of multiple shad on page 13a of marpa.

While the .conllu outputs now put such shad sequences in the same "sentence", the Other_Dependencies grammar makes each shad a delimiter and so only marks the dependency for the first shad in a sequence.