Fix label for "remove cut" buttons

[LukasKalbertodt]

I am not sure what the initial intention was here, but I guess we don't
really need different labels for the two different buttons. Helps
keeping the translation strings to a minimum. Before this commit, the
"remove end" button did not have any translation and showed the
translation key.

[JulianKniephoff]

review-remove-${marker}-end was probably a typo and was supposed to be just review-remove-${marker}, and the intention was to be able to translate the two labels independently, which I still think is the right thing to do, although I wouldn't mind unifying them, either, in a simple case like this.

However, if this is only about saving translations, may I direct your attention to i18next's "nesting" feature. With that, you could have

  "review-remove-start": "Remove",
  "review-remove-end": "$t(review-remove-start)",

in the English translation, and then only have to translate review-remove-start in all the languages where the two strings are supposed to be the same, because English is the fallback (presumably?) and nesting is evaluated dynamically.

Another possibility would be to pass the marker as so called context, and then translations could either say

  "review-remove": "Remove",

to unify or

  "review-remove_start": "Remove start",
  "review-remove_end": "Remove end",

to distinguish.

[LukasKalbertodt]

Went with using contexts now.