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/textprop.c b/src/textprop.c
index 55844d3..fa3830c 100644
--- a/src/textprop.c
+++ b/src/textprop.c
@@ -28,7 +28,7 @@
 
 #include "vim.h"
 
-#if defined(FEAT_TEXT_PROP) || defined(PROTO)
+#if defined(FEAT_PROP_POPUP) || defined(PROTO)
 
 /*
  * In a hashtable item "hi_key" points to "pt_name" in a proptype_T.
@@ -1309,4 +1309,4 @@
     vim_free(prop_lengths);
 }
 
-#endif // FEAT_TEXT_PROP
+#endif // FEAT_PROP_POPUP