Revert 9f94ea4: avoid infinite loop in conestack

This reverts commit 9f94ea4. The original commit was intended to fix an
infinite loop in conetacks, but ended up introducing geometry errors in
long simulations of ionization chambers. Moreover, it appears that the
original issue was incidentally fixed by a different commit.

HEN_HOUSE/egs++/geometry/egs_cones/egs_cones.h

@@ -1554,12 +1554,6 @@ class EGS_ConeStack : public EGS_BaseGeometry {
                 t = tp;                             // set t = distance to plane
             }
 
-            // If we are right on a plane, return -1
-            if(tp < boundaryTolerance) {
-                t = 0;
-                return -1;
-            }
-
             // distance to outer cone
             int ir = ireg - il*nmax;                // cone index in current layer
             bool hitc = false;                      // assume we don't hit the cone