Fix spelling errors in AGWRegistry.sol, AccountFactory.sol, and hookmanager.test.ts

[Dimitrolito]

• AGWRegistry.sol: Corrected "a AGW account" to "an AGW account" in multiple places.
• AccountFactory.sol: Corrected "a AGW account" to "an AGW account" in multiple places.
• hookmanager.test.ts: Fixed "a execution hook" to "an execution hook" in test descriptions.

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PR-Codex overview

This PR focuses on improving the documentation and correcting minor wording issues in the comments of smart contracts and test files.

Detailed summary

• Updated comment in AccountFactory.sol to correct "a AGW" to "an AGW".
• Updated test description in hookmanager.test.ts from "a execution hook" to "an execution hook" for consistency.
• Updated comment in AGWRegistry.sol to correct "a AGW" to "an AGW" in multiple places.

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