docs: Remove nographic option in runqemu example

Graphic mode is supported for qemuarm-efi and qemuarm64-efi, so use this
by default.

Signed-off-by: Luca Seritan <luca.seritan@huawei.com>

docs/hardware-support/virtual-boards/qemuarm-efi.rst

@@ -50,4 +50,4 @@ Once the image is done, you can run the Qemu using the provided script wrapper:
 
 .. code-block:: console
 
-   $ MACHINE=qemuarm-efi runqemu oniro-image-base nographic slirp
+   $ MACHINE=qemuarm-efi runqemu oniro-image-base slirp

docs/hardware-support/virtual-boards/qemuarm64-efi.rst

@@ -50,4 +50,4 @@ Once the image is done, you can run the Qemu using the provided script wrapper:
 
 .. code-block:: console
 
-   $ MACHINE=qemuarm64-efi runqemu oniro-image-base nographic slirp
+   $ MACHINE=qemuarm64-efi runqemu oniro-image-base slirp