Remove unused private functions

PiperOrigin-RevId: 810776310
Change-Id: I1c67c5efe07c4ca23b04122548b674719be927f7

src/engine/engine_io.c

@@ -1516,7 +1516,7 @@ static void _resetData(const mjModel* m, mjData* d, unsigned char debug_value) {
 
   // clear memory utilization stats
   d->maxuse_stack = 0;
-  mju_zeroSize(d->maxuse_threadstack, mjMAXTHREAD);
+  memset(d->maxuse_threadstack, 0, mjMAXTHREAD*sizeof(mjtSize));
   d->maxuse_arena = 0;
   d->maxuse_con = 0;
   d->maxuse_efc = 0;

src/engine/engine_util_misc.c

@@ -1393,15 +1393,6 @@ void mju_zeroInt(int* res, int n) {
   memset(res, 0, n*sizeof(int));
 }
 
-// set mjtSize vector to 0
-void mju_zeroSize(mjtSize* res, size_t n) {
-  memset(res, 0, n*sizeof(mjtSize));
-}
-
-// set size_t vector to 0
-void mju_zeroSizeT(size_t* res, size_t n) {
-  memset(res, 0, n*sizeof(size_t));
-}
 
 
 // copy int vector vec into res

src/engine/engine_util_misc.h

@@ -142,12 +142,6 @@ MJAPI int mju_isZeroByte(const unsigned char* vec, int n);
 // set integer vector to 0
 MJAPI void mju_zeroInt(int* res, int n);
 
-// set mjtSize vector to 0
-MJAPI void mju_zeroSize(mjtSize* res, size_t n);
-
-// set size_t vector to 0
-MJAPI void mju_zeroSizeT(size_t* res, size_t n);
-
 // copy int vector vec into res
 MJAPI void mju_copyInt(int* res, const int* vec, int n);