Remove deprecated $Rule properties

[BernieWhite]

Description of the issue

Some supporting functions use $Rule.TargetType which is deprecated and will be removed from PSRule v1.

Expected behaviour

Update functions to use $PSRule.TargetType instead.

Module in use and version:

• Module: PSRule.Rules.Azure
• Version: 0.15.0

Captured output from $PSVersionTable:

Name                           Value
----                           -----
PSVersion                      7.0.3
PSEdition                      Core
GitCommitId                    7.0.3
OS                             Microsoft Windows 10.0.19041
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0