chore: fix typos in document (matter-labs#577)

## What ❔

- fixed typo

## Why ❔

fix typos in document

## Checklist

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- [x] PR title corresponds to the body of PR (we generate changelog
entries from PRs).
- [x] Tests for the changes have been added / updated.
- [x] Documentation comments have been added / updated.
- [x] Code has been formatted via `zk fmt` and `zk lint`.
- [x] Spellcheck has been run via `cargo spellcheck
--cfg=./spellcheck/era.cfg --code 1`.

---------

Co-authored-by: Igor Aleksanov <[email protected]>

core/lib/multivm/src/versions/vm_virtual_blocks/utils/overhead.rs

@@ -23,7 +23,7 @@ pub fn derive_overhead(
     let gas_limit = U256::from(gas_limit);
     let encoded_len = U256::from(encoded_len);
 
-    // The MAX_TX_ERGS_LIMIT is formed in a way that may fullfills a single-instance circuits
+    // The MAX_TX_ERGS_LIMIT is formed in a way that may fulfills a single-instance circuits
     // if used in full. That is, within MAX_TX_ERGS_LIMIT it is possible to fully saturate all the single-instance
     // circuits.
     let overhead_for_single_instance_circuits =