[DOCS] Incorrect variable 'abi' in system contracts docs

[huperts]

Brief Description of the Docs Request

An error has been identified in the system contracts docs where the code snippet uses an undefined variable abi, which can lead to runtime issues.

Description of the Documentation You'd Like

The existing docs page should be updated to replace the undefined abi with the properly imported l2OutputOracleProxyABI. This change ensures that the example code runs correctly and interacts with the contract as intended. No new pages are required, only an update to the existing docs to correct the code.

Links to Related Pages

system-contracts.mdx

Additional Context

The issue arises because abi is not defined or imported, which causes a runtime error when trying to use it. I have already submitted a pull request to fix this by replacing abi with l2OutputOracleProxyABI, which was correctly imported. This update will prevent execution errors and ensure the docs provides accurate and functional example code for developers working with Optimism.