Make update-reference-docs.sh OSX compatible.
Make update-reference-docs.sh OSX compatible.

Based on
https://unix.stackexchange.com/questions/663369/invalid-command-code-using-sed-to-replace-characters-inline

Verified this works with OSX 12.5, and Ubuntu 22.04.1.

Signed-off-by: Billy Lynch <051522d0c46404d8ba5b692a10a37b99b8186360@chainguard.dev>

tektoncd/pipeline,tektoncd/pipeline