* test(core/channels_spec): fix flaky test
Always use expect_stdout() to check PTY output.
* test(autocmd/termxx_spec): fix flaky test
Usually the Ctrl-C cancels the following :qa!, but sometimes it doesn't,
and Nvim exits before feed() returns. Instead make sure that :qa! always
reaches Nvim and use expect_exit().
d3aae6172a