[tz] Pedantic correction to Theory regarding size of time zone names

Line 91 of Theory: https://github.com/eggert/tz/blob/master/Theory#L91 reads:

A file name component must not exceed 14 characters …

I found one exception to this rule: The Link: Canada/East-Saskatchewan in backward. East-Saskatchewan is 17 characters. I recommend simply changing the 14 to 17. Howard