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/insexpand.c b/src/insexpand.c
index 121e6ec..4f96174 100644
--- a/src/insexpand.c
+++ b/src/insexpand.c
@@ -1811,7 +1811,7 @@
 	    || c == K_MOUSELEFT || c == K_MOUSERIGHT)
 	return retval;
 
-#ifdef FEAT_TEXT_PROP
+#ifdef FEAT_PROP_POPUP
     // Ignore mouse events in a popup window
     if (is_mouse_key(c))
     {