Add zsh version switch for suffix removal feature

[mgkurtz]

Fixes #797 on older machines by reverting to pre 11f1145 code for old zsh versions.

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I did not look into where the actual incompatibility came from and just tried to

1. revert only the condition,
2. revert only the buffer change
3. revert the whole function

on a 22.04 Ubuntu with zsh 5.8.1.
Only the last option worked, so this is what I suggest.