style(pm_wakeup_sources): Change USB command prefix

The commands for the USB wakeup source all have a prefix of "#". Remove
the "HOST:~$" prefix and add "#" to one of the code blocks since it was
not consistent with the others.

Signed-off-by: Kendall Willis <k-willis@ti.com>

Author: kwillis01

source/linux/Foundational_Components/Power_Management/pm_wakeup_sources.rst

@@ -822,7 +822,7 @@ below command on the Host system
 
 .. code-block:: console
 
-   HOST:~$ lsusb -t
+   # lsusb -t
 
 
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