CSlideShow: Collapse loop into std::all_of

Same behavior, less code. We can also make this function fully
internally linked, given it doesn't depend on instance state.

Runtime/MP1/CSlideShow.hpp

@@ -98,7 +98,6 @@ private:
   bool x135_24_ : 1 = true;
 
   bool LoadTXTRDep(std::string_view name);
-  static bool AreAllDepsLoaded(const std::vector<TLockedToken<CDependencyGroup>>& deps);
 
 public:
   CSlideShow();