don't reset selected slot in toolbelt

Author: ghzdude

src/main/java/gregtech/api/items/toolitem/ItemGTToolbelt.java

@@ -669,7 +669,6 @@ public boolean isItemValid(int slot, @NotNull ItemStack stack) {
 
         @Override
         protected void onContentsChanged(int slot) {
-            if (this.selectedSlot == slot) this.selectedSlot = -1;
             this.updateSlot(slot);
             this.update();