Workaround 2 bugs in the handling of <video> in po4a

https://github.com/mquinson/po4a/issues/178
https://github.com/mquinson/po4a/issues/179

wiki/src/boot_menu_key.inline.html

-<video controls width="640" height="360" poster="https://tails.boum.org/install/inc/videos/boot-menu-key.png">
-  <source src="https://tails.boum.org/install/inc/videos/boot-menu-key.webm" type="video/webm">
-</video>

wiki/src/install/inc/steps/pc_boot_menu.inline.html

@@ -94,7 +94,9 @@ following screenshot is an example of such boot menu:</p>
 
 <p>This animation explains how to use the boot menu key:</p>
 
-[[!inline pages="boot_menu_key.inline" raw="yes" sort="age"]]
+<video controls="true" width="640" height="360" poster="https://tails.boum.org/install/inc/videos/boot-menu-key.png">
+  <source src="https://tails.boum.org/install/inc/videos/boot-menu-key.webm" type="video/webm" />
+</video>
 
 <h3>Check our list of known issues</h3>