patch 8.0.1718: terminal scrollback test fails on MS-Windows

Problem:    Terminal scrollback test fails on MS-Windows.
Solution:   Check for the last line of output anticipating there might be an
            empty line below it.
diff --git a/src/testdir/test_terminal.vim b/src/testdir/test_terminal.vim
index 6e101cf..5f330f7 100644
--- a/src/testdir/test_terminal.vim
+++ b/src/testdir/test_terminal.vim
@@ -281,7 +281,8 @@
     call term_sendkeys(buf, "cat Xtext\<CR>")
   endif
   let rows = term_getsize(buf)[0]
-  call WaitFor({-> term_getline(buf, rows - 1) =~ '149'})
+  " On MS-Windows there is an empty line, check both last line and above it.
+  call WaitFor({-> term_getline(buf, rows - 1) . term_getline(buf, rows - 2) =~ '149'})
   let lines = line('$')
   call assert_inrange(91, 100, lines)