Portenta X8: Flashing: Fix wording

Use 'booting' instead of 'flashing' as at the moment we are past
the flashing stage.

Signed-off-by: Vanessa Maegima <vanessa.maegima@foundries.io>

Author: vanmaegima

content/hardware/04.pro/boards/portenta-x8/tutorials/image-flashing/content.md

@@ -101,7 +101,7 @@ Switch back the DIP switches to OFF position.
 
 Unplug and then plug in the Portenta X8 to your computer.
 
-***After flashing you will need to wait 10 secs, until the Portenta X8 blue LED starts blinking, this means the boot was successful***
+***After booting you will need to wait 10 secs, until the Portenta X8 blue LED starts blinking, this means the boot was successful***
 
 ## Troubleshooting