Remove remaining aliases deprecated in 0.12.0

[pquentin]

I still need a news fragment, but I'll wait for #1593 to go through. And I guess I'll add the newsfragment for #1594 here too.

[codecov]

Codecov Report

Merging #1596 into master will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1596   +/-   ##
=======================================
  Coverage   99.69%   99.69%           
=======================================
  Files         109      110    +1     
  Lines       13810    13858   +48     
  Branches     1054     1062    +8     
=======================================
+ Hits        13768    13816   +48     
  Misses         27       27           
  Partials       15       15           

Impacted Files	Coverage Δ
trio/__init__.py	100.00% <ø> (ø)
trio/_threads.py	100.00% <0.00%> (ø)
trio/_core/_ki.py	100.00% <0.00%> (ø)
trio/_core/__init__.py	100.00% <0.00%> (ø)
trio/testing/__init__.py	100.00% <0.00%> (ø)
trio/tests/test_socket.py	100.00% <0.00%> (ø)
trio/tests/test_testing.py	100.00% <0.00%> (ø)
trio/tests/test_threads.py	100.00% <0.00%> (ø)
trio/_core/_thread_cache.py	100.00% <0.00%> (ø)
trio/_core/_wakeup_socketpair.py	100.00% <0.00%> (ø)
... and 9 more

[pquentin]

Please take another look.