patch 8.1.2371: FEAT_TEXT_PROP is a confusing name

Problem:    FEAT_TEXT_PROP is a confusing name.
Solution:   Use FEAT_PROP_POPUP. (Naruhiko Nishino, closes #5291)
diff --git a/src/testdir/test_execute_func.vim b/src/testdir/test_execute_func.vim
index 2f02409..c2d504f 100644
--- a/src/testdir/test_execute_func.vim
+++ b/src/testdir/test_execute_func.vim
@@ -90,7 +90,7 @@
   let line = win_execute(otherwin, 'echo getline(1)')
   call assert_match('the new window', line)
 
-  if has('textprop')
+  if has('popupwin')
     let popupwin = popup_create('the popup win', {'line': 2, 'col': 3})
     redraw
     let line = 'echo getline(1)'->win_execute(popupwin)