doc: uefi: remove ".py" suffix for pytest.py command

the file pytest.py does not exist

Signed-off-by: Wei Ming Chen <jj251510319013@gmail.com>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/doc/develop/uefi/uefi.rst b/doc/develop/uefi/uefi.rst
index c739242..0389b26 100644
--- a/doc/develop/uefi/uefi.rst
+++ b/doc/develop/uefi/uefi.rst
@@ -193,7 +193,7 @@
 .. code-block:: bash
 
     cd <U-Boot source directory>
-    pytest.py test/py/tests/test_efi_secboot/test_signed.py --bd sandbox
+    pytest test/py/tests/test_efi_secboot/test_signed.py --bd sandbox
 
 UEFI binaries may be signed by Microsoft using the following certificates: