docs: fix incorrect default values in configuration.mdx

[Forostovec]

docs: fix incorrect default values in configuration.mdx

Updated several default configuration values in the documentation that didn't match the actual implementation:

• sender_recovery commit_threshold was 100k, should be 5M (crates/config/src/config.rs:262)
• execution max_cumulative_gas had wrong value (off by 1000x) and incorrect calculation comment (crates/config/src/config.rs:294)
• merkle section was completely outdated - replaced deprecated clean_threshold with actual fields: incremental_threshold (7k) and rebuild_threshold (100k) (crates/config/src/config.rs:349-366)
• peers refill_slots_interval was showing 1s instead of actual 5s default (crates/net/network-types/src/peers/config.rs:180)

These mismatches would confuse users trying to understand or customize their node configuration.