Revert "Support for querying Bitcoin/Litecoin prices via F::Q's MtGox module"

This reverts commit r22988.
See https://bugzilla.gnome.org/show_bug.cgi?id=698769#c8

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@23119 57a11ea4-9604-0410-9ed3-97b8803252fd