fix: reduce RPC concurrency to prevent rate limit errors

[fakedev9999]

Reduces RPC concurrency to prevent rate limit errors in validity proposer.

op-succinct proposer was making up to 2,000 concurrent RPC calls when creating range proof requests, causing HTTP 429 rate limit errors from l2 nodes. With 1800-block ranges, this resulted in 36,000 total RPC calls for 10 range requests in a burst.

Reduced concurrency of block data fetching from 100 to 10 concurrent blocks

This limits peak concurrent RPC calls to 100 instead of 2,000, preventing rate limit errors while maintaining reasonable performance and stability of the proposer.

[github-actions]

Metric	Value
Batch Start	7,377,756
Batch End	7,377,761
Witness Generation (seconds)	0
Execution Duration (seconds)	57
Total Instruction Count	1,370,174,182
Oracle Verify Cycles	155,254,039
Derivation Cycles	1,092,725,878
Block Execution Cycles	7,169,689
Blob Verification Cycles	23,288,884
Total SP1 Gas	1,972,611,370
Number of Blocks	5
Number of Transactions	5
Ethereum Gas Used	239,168
Cycles per Block	274,034,836
Cycles per Transaction	274,034,836
Transactions per Block	1
Gas Used per Block	47,833
Gas Used per Transaction	47,833
BN Pair Cycles	0
BN Add Cycles	0
BN Mul Cycles	0
KZG Eval Cycles	0
EC Recover Cycles	0
P256 Verify Cycles	0

[Hamzaraza351]

Great but don't give so much