vim-patch:8.0.1262: terminal redir test is flaky

Problem:    Terminal redir test is flaky.
Solution:   Add it to the list of flaky tests.

7dd88c5133

src/nvim/testdir/runtest.vim

@@ -222,6 +222,7 @@ endif
 let s:flaky = [
       \ 'Test_oneshot()',
       \ 'Test_terminal_composing_unicode()',
+      \ 'Test_terminal_redir_file()',
       \ 'Test_with_partial_callback()',
       \ 'Test_lambda_with_timer()',
       \ ]