[infoscanner] remove whitespaces from sample scan exclude regexs (fixes #15605)

This commit removes leading and trailing whitespaces from the movies and tvshows
exclude from scan regular expressions. Impact - if any - should be pretty low as
samples usually reside in a dedicated samples folder or are following naming
conventions where the word sample is either pre- or postfixed to the actual media.

Not sure how non-scene handles though. Might raise yet other regressions in case
someone thinks separating with space is a good idea. Even though i put up this PR,
i'd vote for not including it ;)

@topfs2, @MartijnKaijser for decision whether to include or not.