Fix unsubscribe and add a test

[samlior]

Description

Fix unsubscribe and add a test.
#3992

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• I have selected the correct base branch.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• Any dependent changes have been merged and published in downstream modules.
• I ran npm run dtslint with success and extended the tests and types if necessary.
• I ran npm run test:unit with success.
• I ran npm run test:cov and my test cases cover all the lines and branches of the added code.
• I ran npm run build and tested dist/web3.min.js in a browser.
• I have tested my code on the live network.
• I have checked the Deploy Preview and it looks correct.
• I have updated the CHANGELOG.md file in the root folder.

[samlior]

@spacesailor24

[coveralls]

Pull Request Test Coverage Report for Build 1210555715

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 422 unchanged lines in 7 files lost coverage.
• Overall coverage decreased (-2.6%) to 72.908%

---

Files with Coverage Reduction	New Missed Lines	%
packages/web3-core-requestmanager/src/jsonrpc.js	1	88.0%
packages/web3-core-helpers/src/formatters.js	24	80.65%
packages/web3-core-helpers/src/errors.js	31	4.41%
packages/web3-utils/src/soliditySha3.js	55	5.13%
packages/web3-utils/src/index.js	62	29.31%
packages/web3-utils/src/utils.js	85	13.04%
packages/web3-eth-accounts/src/index.js	164	25.31%

Totals
Change from base Build 1195730440:	-2.6%
Covered Lines:	3324
Relevant Lines:	4310

---

💛 - Coveralls

[github-actions]

This PR has been automatically marked as stale beacause it has not had recent activity. It will be closed in 7 days if no further activity occurs. Thank you for your contributions. If you believe this was a mistake, please comment.

[spacesailor24]

Thank you for opening this PR, apologies it took so long to be looked at

Test failure is unrelated to changes, this looks good minus the CHANGELOG.md needing to be updated (but I can take care of that)

I believe the test failure is related to #3816, I will be working on updating our tests so this is unblocked

Thank you for your patience