[inputstream] remove inputstreamaddon and inputstreamclass as identifiers for inputstream addons

[phunkyfish]

Description

Remove inputstreamaddon and inputstreamclass as identifiers for inputstream addons

Motivation and Context

They are no longer required and it is past the end of May as stated in the forum thread here: https://forum.kodi.tv/showthread.php?tid=353560

How Has This Been Tested?

On mac, using iptv simple.

Screenshots (if appropriate):

Types of change

• Bug fix (non-breaking change which fixes an issue)
• Clean up (non-breaking change which removes non-working, unmaintained functionality)
• Improvement (non-breaking change which improves existing functionality)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that will cause existing functionality to change)
• Cosmetic change (non-breaking change that doesn't touch code)
• None of the above (please explain below)

Checklist:

• My code follows the Code Guidelines of this project
• My change requires a change to the documentation, either Doxygen or wiki
• I have updated the documentation accordingly
• I have read the Contributing document
• I have added tests to cover my change
• All new and existing tests passed

[AlwinEsch]

Thanks a lot for cleanup!