tools: ynl: check for membership with 'not in'

It is better to use 'not in' instead of 'not {element} in {collection}'
according to Ruff.

This is linked to Ruff error E713 [1]:

  Testing membership with {element} not in {collection} is more readable.

Link: https://docs.astral.sh/ruff/rules/not-in-test/ [1]
Signed-off-by: Matthieu Baerts (NGI0) <[email protected]>
Reviewed-by: Donald Hunter <[email protected]>
Reviewed-by: Asbjørn Sloth Tønnesen <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: matttbe

tools/net/ynl/pyynl/ynl_gen_c.py

@@ -638,7 +638,7 @@ def _attr_typol(self):
         return '.type = YNL_PT_BITFIELD32, '
 
     def _attr_policy(self, policy):
-        if not 'enum' in self.attr:
+        if 'enum' not in self.attr:
             raise Exception('Enum required for bitfield32 attr')
         enum = self.family.consts[self.attr['enum']]
         mask = enum.get_mask(as_flags=True)