Remove dead code XDomainRequest reference

[benjamingr]

There is an XDomainRequest reference here from 7f772ef#diff-5b5ca1c2ac7acf4ca9be5b53329cc1a2 but this only works in IE9 and IE10 which don't have MSE anyway and aren't supported by hls.js

Remove this tidbit of dead code.

[mangui]

thanks @benjamingr
the issue is that these lines have been added on purpose
see #185 (comment)
I am bit reluctant to remove them
ping @mimse

[benjamingr]

Hi @mangui - thanks for the review.

XDomainRequest is not defined in IE11 to begin (not on Windows 7 and not on Windows 8.1).

I just checked with BrowserStack:

I'm afraid no code has ever entered this path in hls.js :) This is a good thing, since XDomainRequest has completely different semantics for CORS - for example you can't use it to read an array buffer (IIRC it's only text data, and no additional headers or something silly like that).

[mangui]

thanks @benjamingr fair enough, i am going to merge next week unless @mimse gives rationale until then