patch 8.2.3534: autoread test is a bit flaky

Problem:    Autoread test is a bit flaky.
Solution:   Wait a brief moment before overwriting the file.

src/testdir/test_stat.vim

@@ -104,7 +104,8 @@ func Test_autoread_fast()
   setlocal autoread
   call setline(1, 'foo')
   w!
-  silent !echo bar > Xautoread
+  sleep 10m
+  call writefile(['bar'], 'Xautoread')
   sleep 10m
   checktime
   call assert_equal('bar', trim(getline(1)))

src/version.c

@@ -757,6 +757,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3534,
 /**/
     3533,
 /**/