Report script returns historic total of mech calls in total column

[dagacha]

The script trades.py alway returns historic total of mech calls in the total column.

[How it is observed]

Running the command

cd trader; poetry run python ../trades.py --creator YOUR_SAFE_ADDRESS --from-date DATE1 --to-date DATE2; cd ..

always returns the same expense in Mech calls in the total column.

[jmoreira-valory]

Addressed in #248