[fix] modular setup macro padding

[luffykai]

Currently, if the modulus has 40 bytes, the blocksize is 8 and final number of limbs is still 40.
But we can't really do 40, as the adapter is either 32 or 48. Change the macro to match that logic

[github-actions]

group	app.proof_time_ms	app.cycles	app.cells_used	leaf.proof_time_ms	leaf.cycles	leaf.cells_used
verify_fibair	(-63 [-2.7%]) 2,233	513,774	19,386,023	-	-	-
fibonacci_program	(+35 [+0.6%]) 6,060	1,500,137	51,487,838	-	-	-
regex_program	(-34 [-0.2%]) 17,829	4,190,904	165,010,909	-	-	-
ecrecover_program	(+18 [+0.7%]) 2,613	285,401	15,075,033	-	-	-

Commit: f0502f0

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