Remove unnecessary use of failure::Fail

src/configure/auto_mozilla.rs

@@ -1,8 +1,6 @@
 //! # Thunderbird's Autoconfiguration implementation
 //!
 //! Documentation: https://developer.mozilla.org/en-US/docs/Mozilla/Thunderbird/Autoconfiguration */
-use failure::Fail;
-
 use quick_xml;
 use quick_xml::events::{BytesEnd, BytesStart, BytesText};