Merge pull request #6790 from justinmk/oldtest

oldtests: Mark Test_lambda_with_timer as flaky

src/nvim/testdir/runtest.vim

@@ -137,6 +137,7 @@ endif
 let s:flaky = [
       \ 'Test_with_partial_callback()',
       \ 'Test_oneshot()'
+      \ 'Test_lambda_with_timer()'
       \ ]
 
 " Locate Test_ functions and execute them.