Removed branch protection rule

Hi,

I added the “signed commits” branch protection rule to the qtspecs
repository because

(1) GitHub was making frightening sounding pronouncements about
    repositories that don’t have any branch protection rules.
(2) I thought signed commits would be easy for everyone to do.

I was wrong on (2) and Christian has advocated for removing the rule
because it limits who among the editors can perform merges.

So I’ve removed it. 

I’ll try not to feel dirty every time GitHub whispers about the
impending downfall of civilization because we have unprotected branches.

                                        Be seeing you,
                                          norm

--
Norm Tovey-Walsh
Saxonica