[docs] [issue28763] Use en-dashes for ranges in docs

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

Some of these double hyphens are in code examples. Thus the actual number of en-dashes that can be changed to em-dashes is smaller.

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue28763>
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