Removed an unused and unavailable class member

Signed-off-by: Florian Fleissner <florian.fleissner@inpartik.de>

src/kaleidoscope/plugin/Heatmap.cpp

@@ -33,8 +33,7 @@ uint8_t Heatmap::heat_colors_length = 4;
 uint16_t Heatmap::update_delay = 1000;
 
 Heatmap::TransientLEDMode::TransientLEDMode(const Heatmap *parent)
-  : parent_(parent),
-    // store the number of times each key has been strock
+  : // store the number of times each key has been strock
     heatmap_{},
     // max of heatmap_ (we divide by it so we start at 1)
     highest_(1),

src/kaleidoscope/plugin/Heatmap.h

@@ -57,8 +57,6 @@ class Heatmap : public Plugin,
 
    private:
 
-    const Heatmap *parent_;
-
     uint16_t heatmap_[Kaleidoscope.device().numKeys()];
     uint16_t highest_;
     uint16_t last_heatmap_comp_time_;