docs(contracts): OZ-N07 Missing or Inconsistent Documentation

[zimpha]

Purpose or design rationale of this PR

This PR fix the following issue reported by Openzepplin: N-07 Missing or Inconsistent Documentation

Throughout the codebase, there are inconsistencies in the documentation. Particularly when checking the NatSpec docstrings from the other analogous set of contracts:

• At lines 47 and 57 of the L1ERC721Gateway contract, "in L1" is missing at the end. The same happens at lines 47 and 54 of the L1ERC1155Gateway contract, at lines 47, 48, 63 and 64 of the L1CustomERC20Gatewaycontract, and at lines 57, 58, 81 and 82 of the L1USDCGateway contract.
• The L1WETHGateway contract misses the same statement present in the L2WETHGateway contract about parameters not being used.
• The L2ETHGateway contract is missing documentation in the _withdraw function analogous to the one in L1ETHGateway._deposit but with the respective parameters.
• The L2GatewayRouter is missing the "@dev This variable is no longer used" comment in the ethGateway variable definition.
• In the IL2GasPriceOracle interface, the two added getter functions do not have any documentation besides a single "@notice" comment.

Consider fixing the reported examples to improve the overall readability of the codebase.

PR title

Your PR title must follow conventional commits (as we are doing squash merge for each PR), so it must start with one of the following types:

• docs: Documentation-only changes

Deployment tag versioning

Has tag in common/version.go been updated or have you added bump-version label to this PR?

• No, this PR doesn't involve a new deployment, git tag, docker image tag
• Yes

Breaking change label

Does this PR have the breaking-change label?

• No, this PR is not a breaking change
• Yes

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (999db62) 57.04% compared to head (97d547e) 57.04%.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1098   +/-   ##
========================================
  Coverage    57.04%   57.04%           
========================================
  Files          150      150           
  Lines        11181    11181           
========================================
  Hits          6378     6378           
  Misses        4358     4358           
  Partials       445      445           

Flag	Coverage Δ
contracts	57.36% <ø> (ø)

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