Update Solid and Shell plugins to use FlexComp.

PiperOrigin-RevId: 573755821
Change-Id: I3b8d7fb27f0e940038fa9fd2b26ecc746df4f7ac

plugin/elasticity/elasticity.cc

@@ -18,7 +18,6 @@
 #include <cstdlib>
 #include <sstream>
 #include <string>
-#include <utility>
 #include <vector>
 #include <mujoco/mujoco.h>
 
@@ -47,19 +46,4 @@ bool CheckAttr(const char* name, const mjModel* m, int instance) {
   return end == value.data() + value.size();
 }
 
-mjtNum SquaredDist3(const mjtNum pos1[3], const mjtNum pos2[3]) {
-  mjtNum dif[3] = {pos1[0]-pos2[0], pos1[1]-pos2[1], pos1[2]-pos2[2]};
-  return dif[0]*dif[0] + dif[1]*dif[1] + dif[2]*dif[2];
-}
-
-void UpdateSquaredLengths(std::vector<mjtNum>& len,
-                          const std::vector<std::pair<int, int> >& edges,
-                          const mjtNum* x) {
-  for (int e = 0; e < len.size(); e++) {
-    const mjtNum* p0 = x + 3*edges[e].first;
-    const mjtNum* p1 = x + 3*edges[e].second;
-    len[e] = SquaredDist3(p0, p1);
-  }
-}
-
 }  // namespace mujoco::plugin::elasticity