Add .net to context selector to skip live envs

What does this MR do and why?

Cherry-picking merge request !129803 (merged) per discussion in #422681 (comment 1521088643)

Adding .net to context selector to ensure that specs marked with :skip_live_env are skipped against Release environment.

Context - #422681 (comment 1521005633), one of the specs was recently promoted to Reliable but it has skip_live_env which is ignoring the skip since Release is on https://release.gitlab.net/ .

How to set up and validate locally

See original MR - !129803 (merged)

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