patch 8.1.1934: not enough tests for text property popup window

Problem:    Not enough tests for text property popup window.
Solution:   Add a few more tests.
diff --git a/src/popupwin.c b/src/popupwin.c
index bf12055..4dadee6 100644
--- a/src/popupwin.c
+++ b/src/popupwin.c
@@ -1103,7 +1103,7 @@
 	    wantcol = screen_ecol + wantcol;
 	else
 	    // left of the text
-	    wantcol = screen_scol + wantcol - 1;
+	    wantcol = screen_scol + wantcol - 2;
     }
 
     if (wp->w_popup_pos == POPPOS_CENTER)