SCORU/Node: fix bug in Arith PVM eval_many for dissections
Context
The off-by one error made the interpreter think the PVM consumed more ticks than allowed and so would generate incorrect dissections.
(Dissection traces were generated without the optimized dissection computation of !6948 (merged).)
Manually testing the MR
dune exec tezt/tests/main.exe -- -f sc_rollup.ml arith regression refutation
Edited by Alain Mebsout