fix: Make group announcements work without TCP requirement

[JFreegman]

This change is 

[codecov]

Codecov Report

Merging #1570 into ngc will increase coverage by 0.46%.
The diff coverage is 44.70%.

@@            Coverage Diff             @@
##              ngc    #1570      +/-   ##
==========================================
+ Coverage   80.83%   81.29%   +0.46%     
==========================================
  Files          95       95              
  Lines       20515    20524       +9     
==========================================
+ Hits        16583    16685     +102     
+ Misses       3932     3839      -93     

Impacted Files	Coverage Δ
toxcore/group_chats.c	67.99% <31.14%> (+2.71%)	⬆️
toxcore/Messenger.c	86.13% <77.27%> (-0.08%)	⬇️
toxcore/group_announce.c	92.02% <100.00%> (-0.12%)	⬇️
toxav/bwcontroller.c	42.10% <0.00%> (-7.90%)	⬇️
toxcore/net_crypto.c	94.23% <0.00%> (-0.37%)	⬇️
toxav/toxav.c	69.09% <0.00%> (-0.23%)	⬇️
toxcore/TCP_connection.c	76.75% <0.00%> (+0.18%)	⬆️
toxcore/friend_connection.c	95.53% <0.00%> (+1.11%)	⬆️
auto_tests/toxav_basic_test.c	85.54% <0.00%> (+1.60%)	⬆️
toxcore/TCP_client.c	64.76% <0.00%> (+2.59%)	⬆️
... and 3 more

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