Log Message:
thunderbird: Update to 68.9.0

Changelog:
Fixes
fixed Custom headers added for searching or filtering could not be removed
fixed Calendar: Today Pane updated prior to loading all data
fixed Stability improvements
fixed Various security fixes

Security fixes:
#CVE-2020-12399: Timing attack on DSA signatures in NSS library
#CVE-2020-12405: Use-after-free in SharedWorkerService
#CVE-2020-12406: JavaScript Type confusion with NativeTypes
#CVE-2020-12410: Memory safety bugs fixed in Thunderbird 68.9.0
#CVE-2020-12398: Security downgrade with IMAP STARTTLS leads to information leakage