patch 9.0.0539: long message test can be flaky

Problem:    Long message test can be flaky.
Solution:   Wait for more prompt instead of ruler.

src/testdir/test_messages.vim

@@ -366,7 +366,8 @@ func Test_quit_long_message()
     echom range(9999)->join("\x01")
   END
   call writefile(content, 'Xtest_quit_message')
-  let buf = RunVimInTerminal('-S Xtest_quit_message', #{rows: 6})
+  let buf = RunVimInTerminal('-S Xtest_quit_message', #{rows: 6, wait_for_ruler: 0})
+  call WaitForAssert({-> assert_match('^-- More --', term_getline(buf, 6))})
   call term_sendkeys(buf, "q")
   call VerifyScreenDump(buf, 'Test_quit_long_message', {})
 

src/version.c

@@ -699,6 +699,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    539,
 /**/
     538,
 /**/