Log Message:
thunderbird: Update to 78.9.0

Changelog:
Fixes
New mail notification displayed old messages that were unread

Spaces following soft line breaks in messages using quoted-printable and format
=flowed were incorrectly encoded; existing messages which were previously
incorrectly encoded may now display with some words not separated by a space

Some fields were unreadable in the Dark theme in the General preferences panel

Sending a message containing an anchor tag with an invalid data URI failed

When switching tabs, input focus was not moved to the new tab

Address Book: Syncing a read-only Google address book via CardDAV failed

Address Book: Importing VCards with non-ascii characters would fail

Address Book: Some values may not have been parsed when syncing from Google
address books.

Add-ons Manager did not show if an addon used experiment APIs

Calendar: Removing a recurring task was not possible

Various security fixes

Security fixes:
#CVE-2021-23981: Texture upload into an unbound backing buffer resulted in an
 out-of-bound read
#MOZ-2021-0002: Angle graphics library out of date
#CVE-2021-23982: Internal network hosts could have been probed by a malicious
 webpage
#CVE-2021-23984: Malicious extensions could have spoofed popup information