Spoilers end here.
Simply transcludes {{CollapseEnd}} with default text Spoilers end here.
The label text can still be changed using the same parameters as CollapseEnd, meaning this templates works in the exact same way except for having a default value.
The reason for this separate template is to allow an empty label value for CollapseEnd while maintaining the old function of this template (SpoilerSectionEnd), which CollapseEnd was based on.
Note: {{SpoilerSectionStart}} is a standard redirect to {{CollapseStart}}, which has Spoilers: as a default value.