[frogr] Fixed error in the instructions to create a flatpak

[Mario Sanchez Prada <msanchez src gnome org>]

commit 84739cdefc501c5b7e5e4ccaf87ff2cbe950408a
Author: Mario Sanchez Prada <msanchez gnome org>
Date:   Wed Oct 5 14:52:23 2016 +0100

    Fixed error in the instructions to create a flatpak

 flatpak/README.md |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/flatpak/README.md b/flatpak/README.md
index 7521eae..2a2d5c7 100644
--- a/flatpak/README.md
+++ b/flatpak/README.md
@@ -48,5 +48,5 @@ Note that if you do further changes in the `appdir` (e.g. to the metadata), you'
 
 Last, you can bundle frogr to a file with the `build-bundle` subcommand:
 ```
-  flatpak build-bundle repo frogr.bundle org.gnome.Frogr
+  flatpak build-bundle repo org.gnome.Frogr.flatpak org.gnome.Frogr
 ```