ComponentRepeat: remove firsts_cache, precalc code

Firsts are easy to compute in ComponentRepeat::first() now.

src/parser/ComponentRepeat.h

@@ -120,8 +120,6 @@ public:
     enum RepeatType type;
 
 protected:
-    /** Called by \ref buildFollowSet to connect up the various repeats. */
-    void precalc_firsts();
     void postSubNotePositionHook();
     void wireRepeats(GlushkovBuildState &bs);
 
@@ -134,8 +132,6 @@ protected:
     Position posFirst;
     Position posLast;
 
-    std::vector<PositionInfo> firsts_cache;
-
     ComponentRepeat(const ComponentRepeat &other);
 };