Change wording in Night Light KCM to reflect science not folklore

Summary: Until there's conclusive science that color temperature affects eye strain, KDE should not make any such claims.

Full text: There is no scientific evidence that blue light from computer monitors has anything to do with eye strain (or sleep patterns). This is folklore based on some faulty research from decades ago that somehow made it into the main stream. Color temperature ends up being just a matter of personal preference. Actual studies (using lenses) showed that blocking blue light did not help people who suffer from eye strain at all (a tldr of many studies is this: https://pubmed.ncbi.nlm.nih.gov/29044670/).

The Keywords line is untouched on purpose. People looking for those terms should not be led to believe that the feature itself was removed.

Some other links (digested for popular science): https://onezero.medium.com/blue-light-isnt-as-bad-as-you-think-d9e1e48f0cc6 and https://time.com/5752454/blue-light-sleep/