Resolve compiler warning by removing unused line

[Levi0804]

Description

This PR removes an unused line from the unit test test_events in the account module (aptos-move/framework/aptos-framework/sources/account.move):
let eventhandle = &borrow_global<Account>(addr).coin_register_events;

How to generate the warning?

To generate the warning, create a module and bring the account module into scope. For example:

module 0x9000::test {
    use aptos_framework::account;
}

now use aptos move test, the following warning could be seen:

warning[W09003]: unused assignment
     ┌─ /home/levi0804/.move/https___github_com_aptos-labs_aptos-core_git_mainnet/aptos-move/framework/aptos-framework/sources/account.move:1538:13
     │
1538 │         let eventhandle = &borrow_global<Account>(addr).coin_register_events;
     │             ^^^^^^^^^^^ Unused assignment or binding for local 'eventhandle'. Consider removing, replacing with '_', or prefixing with '_' (e.g., '_eventhandle')

How Has This Been Tested?

I removed the mentioned line locally from the unit test in the account module and ran aptos move test --skip-fetch-latest-git-deps on a module similar to the one above (0x9000::test), which resolved the compiler warning

Type of Change

• New feature
• Bug fix
• Breaking change
• Performance improvement
• Refactoring
• Dependency update
• Documentation update
• Tests

[trunk-io]

⏱️ 17m total CI duration on this PR

Job	Cumulative Duration	Recent Runs
rust-move-tests	12m	🟩
rust-cargo-deny	2m	🟩
check-dynamic-deps	1m	🟩
semgrep/ci	29s	🟩
general-lints	25s	🟩
file_change_determinator	12s	🟩
permission-check	6s	🟥 🟩
permission-check	5s	🟥 🟩

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[gregnazario]

Doing the real work that kept bothering me :)