[firefox] Upcoming string changes for Firefox 70

Hi,

In the past days we found a couple of bugs that will require string changes
to Beta (70). The new strings will show up in Pontoon in the next hour, but
I want to point out a few important details beforehand.

*Protection Levels in Preferences (bug 1579705)*

In 69 we had 3 levels of Content Blocking (Standard, Strict, Custom). In 70
the section name of Preferences was updated from "Content Blocking" to
"Enhanced Tracking Protection", but the level names were kept unchanged.

Since these level names are adjectives, if your language has genders, you
might end up with a mismatch. For example, in Italian "Content Blocking" is
male, so the level is "Personalizzato", but "Enhanced Tracking Protection"
is female, and it would need "Personalizzata".

To minimize the impact of this change, we created a migration that will
copy the existing translation over the new strings. Unlike other
migrations, where we run the migration before exposing the strings in
Pontoon, I plan to run this migration in about a week from now, in order to
give affected locales some time to catch up, and add a different
translation if needed.

Thanks to Michal Stanke for raising the issue.

*Reused accesskey (bug 1579730)*

The label "Manage Content Blocking" was updated to "Manage Protection
Settings", but the existing accesskey was reused. You'll find a new
accesskey (contentBlocking.manageSettings2.accesskey) for this label.
https://transvision.mozfr.org/?recherche=contentBlocking.manageSettings2&repo=gecko_strings&sourcelocale=en-US&locale=en-US&search_type=strings_entities

Also a reminder that Transvision has a view to check for accesskey errors,
if they're translated in your locale.
https://transvision.mozfr.org/accesskeys/

Thanks to :aryx for reporting the issue.

*New Certificate Viewer*

In the next batch of new strings you'll also find the new certificate
viewer available on Nightly. There are still a lot of strings hard-coded
(all the section titles), and there's already a bug on file for it.

Francesco