patch 8.2.0533: tests using term_wait() can still be flaky

Problem:    Tests using term_wait() can still be flaky.
Solution:   Increase the wait time when rerunning a test. (James McCoy,
            closes #5899)  Halve the initial times to make tests run faster
            when there is no rerun.
diff --git a/src/testdir/test_debugger.vim b/src/testdir/test_debugger.vim
index 8ba3998..a99154a 100644
--- a/src/testdir/test_debugger.vim
+++ b/src/testdir/test_debugger.vim
@@ -8,7 +8,7 @@
 " If the expected output argument is supplied, then check for it.
 func RunDbgCmd(buf, cmd, ...)
   call term_sendkeys(a:buf, a:cmd . "\r")
-  call term_wait(a:buf, 20)
+  call TermWait(a:buf)
 
   if a:0 != 0
     " Verify the expected output