Fix method signature mismatch in Firewall subclass

[jonjitsu]

Description

Fix exception due to method signature mismatch.

Motivation and Context

While using ansible at work last week I got an exception due to the Firewall.element() method not having the same method signature of the parent PanObject class. The PanObject.element() method has two optional kwargs that are used elsewhere. When a Firewall object was passed into one of those code paths that passed in one or both of the kwargs python thew an exception.

The kwargs are unused in the Firewall class and I'm unsure how those kwargs can be used.

How Has This Been Tested?

We have this package vendored into our repo at work so I patched it for now with the same change.

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist

• [x] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [x] I have added tests to cover my changes if appropriate.
• [x] All new and existing tests passed.