Remove htmlFile validation rule, as it can't possibly work.

[braders]

Overview

Remove htmlFile validation rule, as it can't possibly work.

Before

CRM_Utils_Rule::htmlFile is trying to call CRM_Utils_File::isHtmlFile which doesn't exist (and I can't find any history of it ever existing, although it might have in the SVN days). Therefore, I can't see how this function can possibly work, it makes sense to remove it.

After

htmlFile rule gone.

[civibot]

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[demeritcowboy]

I think it was a typo and meant to be CRM_Utils_File::isHtml(), but regardless I agree it's unused.

And then it looks like maybe so is CRM_Utils_File::isHtml().

And also CRM_Utils_Rule::asciiFile().