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/evalbuffer.c b/src/evalbuffer.c
index a82b897..00185b1 100644
--- a/src/evalbuffer.c
+++ b/src/evalbuffer.c
@@ -565,7 +565,7 @@
 	dict_add_list(dict, "windows", windows);
     }
 
-#ifdef FEAT_TEXT_PROP
+#ifdef FEAT_PROP_POPUP
     // List of popup windows displaying this buffer
     windows = list_alloc();
     if (windows != NULL)