Update tabs.rst

[opto]

for addon manager tab created by extra->addons, the title also isn't there yet (it is 'loading...')

[jobisoft]

This has to be changed in the source of Thunderbird.

Do you want to file the bug and the patch yourself to have this noted as your contribution?

[opto]

yes, I can do but may need some advice as to the procedure

[jobisoft]

Handled in: https://bugzilla.mozilla.org/show_bug.cgi?id=1915338