Remove dead Strategy::commandOp

$ rg -w commandOp

src/mongo/s/commands/cluster_explain.h

53:     * TODO(esha): remove once Strategy::commandOp is removed, and make these methods take

src/mongo/s/commands/strategy.cpp

896:void Strategy::commandOp(OperationContext* opCtx,

src/mongo/s/commands/strategy.h

122:    static void commandOp(OperationContext* opCtx,