[pitivi] help: Mention "menu button" rather than "app menu"

[Jean-François Fortin Tam <jfft src gnome org>]

commit 82f24eba824323acc1800204f0a6bf1c4327d13a
Author: Jean-François Fortin Tam <nekohayo gmail com>
Date:   Thu Oct 2 00:43:18 2014 -0400

    help: Mention "menu button" rather than "app menu"
    
    "App menu" could be confused with the global menu that you find in GNOME Shell

 help/C/mainwindow.page |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/help/C/mainwindow.page b/help/C/mainwindow.page
index d3a35f5..dcdc492 100644
--- a/help/C/mainwindow.page
+++ b/help/C/mainwindow.page
@@ -53,9 +53,9 @@
 
     <section>
      <title>Header bar</title>
-      <p>The header bar is a place where basic functions such as <gui>Undo</gui>, <gui>Redo</gui>, 
<gui>Save</gui>, or <gui>Render</gui> can be directly accessed. It also contains the <gui>App menu</gui> 
where you can find further functions such as <gui>New project</gui>, <gui>Open project</gui>, <gui>Project 
settings</gui> or <gui>Preferences</gui>.</p>
+      <p>The header bar is a place where basic functions such as <gui>Undo</gui>, <gui>Redo</gui>, 
<gui>Save</gui>, or <gui>Render</gui> can be directly accessed. It also contains the main <gui>menu 
button</gui> where you can find further functions such as <gui>New project</gui>, <gui>Open project</gui>, 
<gui>Project settings</gui> or <gui>Preferences</gui>.</p>
       <note style="tip">
-          <p>The <gui>App menu</gui> can be opened by pressing <key>F10</key>.</p>
+          <p>The <gui>menu button</gui>'s contents can be accessed by pressing <key>F10</key>.</p>
       </note>
     </section>