[18.0][FIX] auditlog: Remove deprecated name_get methods from models.

[amh-mw]

The name_get method was deprecated in Odoo 17 and removed in Odoo 18.

This was identified by running base module tests on an odoo:18 container with auditlog installed, yielding:

ERROR odoo odoo.addons.base.tests.test_deprecation: FAIL: Subtest TestModelDeprecations.test_name_get (model='auditlog.http.session')
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/odoo/addons/base/tests/test_deprecation.py", line 37, in test_name_get
    self.fail(f"Deprecated name_get method found on {model_name} in {module.__name__}, you should override `_compute_display_name` instead")
AssertionError: Deprecated name_get method found on auditlog.http.session in odoo.addons.auditlog.models.http_session, you should override `_compute_display_name` instead