*/*: update Telegram Desktop: 4.6.5 -> 4.7.0

Also, update:
o) net-im/tg_owt to its recent version;
o) devel/glibmm26: 2.74.0 -> 2.76.0. (*)

Discussed with: fluffy (*)

<ChangeLog>
o) You can disable all resource-intensive animations and animated

stickers and emoji.

o) Power saving mode turns on automatically based on system battery

saving settings.

o) Fully flexible playback speed settings for videos, voice and

video messages.

o) Click the "1X" button to quickly switch between normal and adjusted

speed – or hold it to set any speed between 0.5-2.5x.

o) Improved sound quality for adjusted speed playback.
o) Read receipts in groups under 100 members now show reaction

timestamps and when your messages were read.

o) When inviting people to groups, you can quickly send invite links

to anyone who doesn't allow adding them directly.

o) Invite links now show previews in chats.
o) Fully translatable bots. Bot descriptions and ”What can this bot

do?" sections can now be translated.

o) Starting a call now shows a confirmation window.
o) Fixed pasting images from Firefox on Windows.
o) Global Fn+F shortcut to switch active window to full screen mode

on macOS.

o) Silent notification sound in Focus Mode on macOS.
</ChangeLog>