patch 8.1.1905: cannot set all properties of the info popup

Problem:    Cannot set all properties of the info popup.
Solution:   Add popup_findinfo().  Rename popup_getpreview() to
            popup_findpreview().
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index a64a0b4..aad1bae 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -5808,7 +5808,7 @@
 	}
 # ifdef FEAT_TEXT_PROP
     // Also when 'previewpopup' is empty, it might have been cleared.
-    popup_close_preview(FALSE);
+    popup_close_preview();
 # endif
 }
 #endif