remove old aarch64 CDM workarounds

[HiassofT]

Description

The workarounds were needed to use the ChromeOS library on Linux and are no longer required with the current, native Linux version.

See also emilsvennesson/script.module.inputstreamhelper#647

Note: don't merge this before a new inputstreamhelper version has been released and users had a chance to update their CDM libraries

Motivation and context

Cleanup, get rid of now unneeded code.

How has this been tested?

Running LibreELEC master on RPi5, with CDM 4.10.3057.0 installed via inputstreamhelper.
Tested with the ORF On addon, Livestreams work
Also tested with SlyGuy's Video Test Streams addon, both i.a HLS and Dash with Widevine streams work

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:

• I have read the Contributing document
• My code follows the Code Guidelines of this project
• My change requires a change to the Wiki documentation
• I have updated the documentation accordingly

[HiassofT]

I've switched this PR to draft as I just ran into an issue with the ORF On addon and merging this PR would prevent aarch64 Linux users switching back to older CDM versions.
s0faking/plugin.video.orftvthek#156

Best to wait with the removal until the x86_64/aarch64 Linux CDM issue is fully understood and resolved