doc: clarify that steps also apply to linux for opencl (#18002)

doc: clarify that steps also apply to linux for opencl (#18002)

* Clarify setup steps for Linux

Added note that setup steps apply to Linux as well.

* Added note for backtick replacement

* clarify that backtick replacement only applies on linux

* clarified Linux specific steps

So actually some changes are needed for Linux but they are minor.

* clarify change execution

* clarify by placing info after steps

* clarify which steps

* Make instructions consistent across OSes

* Rm whitespace

* Update docs/backend/OPENCL.md

Co-authored-by: Aaron Teo <redacted>
* Update docs/backend/OPENCL.md

Co-authored-by: Aaron Teo <redacted>
* Update docs/backend/OPENCL.md

Co-authored-by: Aaron Teo <redacted>
---------

Co-authored-by: Aaron Teo <redacted>