src/config/services/index.md: Improve wording

[camoz]

AIUI, this bullet point refers to the clean "environment" of a process, and not to the concept of process state (e.g. running/failed/degraded/...).

[camoz]

Please review carefully, as I'm quite new to runit.

Also note that after my changes it says "[the service] will be started with the same environment variables". I'm not 100% sure this is correct. But if it is, this wording is more precise IMO.

[ericonr]

Looks good, but please fix the commit message to be the same as the PR title.

git commit --amend should allow you to fix the commit message, and then just do git push -f origin patch-1

[camoz]

Done.