Stop exposing the moz-icon URL scheme to the web

We should do this if Mozilla doesn't get to it. https://bugzilla.mozilla.org/show_bug.cgi?id=1222924

added component::applications/tor browser ff60-esr owner::tbb-team priority::high severity::major status::new tbb-fingerprinting type::defect labels

Trac:
Keywords: N/A deleted, tbb-fingerprinting added

Trac:
Priority: Medium to High
Severity: Normal to Major

It seems we will get this with ESR59. However, we want to check that, while it is not allowed any longer to link to moz-icon URLs, the presence of a moz-icon handler is not leaking, see: https://bugzilla.mozilla.org/show_bug.cgi?id=1222924#c14.

Trac:
Keywords: N/A deleted, ff59-esr added

Firefox 60 is the new ESR.

Trac:
Keywords: ff59-esr deleted, ff60-esr added

moved to tpo/applications/tor-browser#23424 (closed)