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/indent.c b/src/indent.c
index 70bb81b..32f1e12 100644
--- a/src/indent.c
+++ b/src/indent.c
@@ -773,7 +773,7 @@
 		// at the start of the indent (replacing spaces with TAB)
 		saved_cursor.col = (colnr_T)(s - newline);
 	}
-#ifdef FEAT_TEXT_PROP
+#ifdef FEAT_PROP_POPUP
 	{
 	    int added = ind_len - (colnr_T)(p - oldline);