Remove unused variables in mapillary/opensfm/opensfm/src/third_party/…

…akaze/lib/AKAZE.cpp

Summary:
LLVM-15 has a warning `-Wunused-but-set-variable` which we treat as an error because it's so often diagnostic of a code issue. Unused variables can compromise readability or, worse, performance.

This diff either (a) removes an unused variable and, possibly, it's associated code, or (b) qualifies the variable with `[[maybe_unused]]`, mostly in cases where the variable _is_ used, but, eg, in an `assert` statement that isn't present in production code.

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Reviewed By: dmm-fb

Differential Revision: D54378379

fbshipit-source-id: 0a23b525ffbe0862e32609ce45af4c2cd7794551

opensfm/src/third_party/akaze/lib/AKAZE.cpp

@@ -269,7 +269,7 @@ void AKAZE::Find_Scale_Space_Extrema(std::vector<cv::KeyPoint>& kpts) {
   double t1 = 0.0, t2 = 0.0;
   float value = 0.0;
   float dist = 0.0, ratio = 0.0, smax = 0.0;
-  int npoints = 0, id_repeated = 0;
+  int id_repeated = 0;
   int sigma_size_ = 0, left_x = 0, right_x = 0, up_y = 0, down_y = 0;
   bool is_extremum = false, is_repeated = false, is_out = false;
   cv::KeyPoint point;
@@ -357,7 +357,6 @@ void AKAZE::Find_Scale_Space_Extrema(std::vector<cv::KeyPoint>& kpts) {
                 point.pt.x *= ratio;
                 point.pt.y *= ratio;
                 kpts_aux.push_back(point);
-                npoints++;
               }
               else {
                 point.pt.x *= ratio;