fix [#33726] keyframe_insert() and keyframe_delete() with index=-1 always fail

The bug was introduced in r53297, was calling pyrna_struct_anim_args_parse() twice for no reason, perhaps baddly applied patch?.


git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@53505 954f8c5b-7b00-dc11-b283-0030488c597c