Improve tests/scripts/depends.py code

As suggested by gilles-peskine-arm.

Co-authored-by: Gilles Peskine <gilles.peskine@arm.com>
Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>

tests/scripts/depends.py

@@ -138,9 +138,7 @@ def restore_config(options):
         shutil.copy(options.config_backup, options.config)
 
 def option_exists(conf, option):
-    if option not in conf.settings:
-        return False
-    return True
+    return option in conf.settings
 
 def set_config_option_value(conf, option, colors, value: Union[bool, str]):
     """Set/unset a configuration option, optionally specifying a value.