See https://github.com/rg3/youtube-dl/pull/9028, especially @lachs0r's comments for the reason behind this change
[NRKTV] Added season and episode number to metadata. [NRKTV] Added category to metadata. [NRKTV] Added tests to NRKTVSeries. [NRKTV] Fixed whitespace issues (flake8).
Closes #11890 Closes #11891 Closes #11892 Closes #11894 Closes #11895 Closes #11897 Closes #11900 Closes #11903 Closes #11904 Closes #11906 Closes #11907 Closes #11909 Closes #11913 Closes #11914 Closes #11915 Closes #11916 Closes #11917 Closes #11918 Closes #11919
NPO websites changed the domain they used for subtitles, from e.omroep.nl to tt888.omroep.nl.