doc: tweak to GSG to fix code-block

Sphinx was complaining about a missing argument, and fixed some trailing
spaces.

Signed-off-by: David B. Kinder <david.b.kinder@intel.com>

doc/getting_started/index.rst

@@ -149,6 +149,7 @@ partition. Follow these steps:
       # efibootmgr -c -l "\EFI\acrn\acrn.efi" -d /dev/sda -p 1 -L ACRN
 
    .. note::
+
       Be aware that a Clearlinux update that includes a kernel upgrade will
       reset the boot option changes you just made. A Clearlinux update could
       happen automatically (if you have not disabled it as described above),
@@ -173,7 +174,7 @@ partition. Follow these steps:
    Here is a more complete example of how to configure the EFI firmware to load the ACRN
    hypervisor and set these parameters.
 
-   .. code-block::
+   .. code-block:: none
 
       # efibootmgr -c -l "\EFI\acrn\acrn.efi" -d /dev/sda -p 1 -L "ACRN Hypervisor" \
             -u "bootloader=\EFI\org.clearlinux\bootloaderx64.efi uart=mmio@0x9141e000"