Fix a missing permission stub in a spec

[agrare]

#20053 removed the stub_vmdb_permission_store_with_types method but a new spec that used that method was added by #20039

Failure: https://travis-ci.com/github/ManageIQ/manageiq/jobs/318274533#L667-L675

Failures:
  1) ExtManagementSystem.supported_types with removed permissions
     Failure/Error:
       stub_vmdb_permission_store_with_types(["ems-type:vmwarews"]) do
         expect(described_class.supported_types).not_to include("vmwarews")
       end
     NoMethodError:
       undefined method `stub_vmdb_permission_store_with_types' for #<RSpec::ExampleGroups::ExtManagementSystem::SupportedTypes:0x00000000300cddb8>
     # ./spec/models/ext_management_system_spec.rb:95:in `block (3 levels) in <top (required)>'

[miq-bot]

Checked commit agrare@6422be7 with ruby 2.5.7, rubocop 0.69.0, haml-lint 0.28.0, and yamllint
1 file checked, 0 offenses detected
Everything looks fine. 🍰

[simaishi]

Jansa backport details:

$ git log -1
commit e514f722d55ba619b5b5eb92bd2b63a7cf9e3fb1
Author: Jason Frey <[email protected]>
Date:   Sat Apr 11 08:56:45 2020 -0400

    Merge pull request #20067 from agrare/fix_missing_vmdb_persmission_stub

    Fix a missing permission stub in a spec

    (cherry picked from commit 5e3484340dd3f5777059ab3d42caa482cc977805)