chore(deps): update codecov/codecov-action action to v4

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
codecov/codecov-action	action	major	v3 -> v4

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Release Notes

codecov/codecov-action (codecov/codecov-action)

### [`v4`](https://togithub.com/codecov/codecov-action/compare/v3...v4) [Compare Source](https://togithub.com/codecov/codecov-action/compare/v3...v4)

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Configuration

📅 Schedule: Branch creation - "before 4am on Monday" (UTC), Automerge - At any time (no schedule defined).

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻ Rebasing: Whenever PR is behind base branch, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

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• [ ] If you want to rebase/retry this PR, check this box

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This PR has been generated by Mend Renovate. View repository job log here.

[github-actions[bot]]

Coverage from tests in ./e2e_test/... for ./consensus/istanbul/... at commit 7ed587be6befe56536afd7cb96e92ae8dcbec06b

coverage: 51.0% of statements across all listed packages

coverage:  63.2% of statements in consensus/istanbul
coverage:  42.8% of statements in consensus/istanbul/announce
coverage:  55.8% of statements in consensus/istanbul/backend
coverage:   0.0% of statements in consensus/istanbul/backend/backendtest
coverage:  24.3% of statements in consensus/istanbul/backend/internal/replica
coverage:  65.7% of statements in consensus/istanbul/core
coverage:  50.0% of statements in consensus/istanbul/db
coverage:   0.0% of statements in consensus/istanbul/proxy
coverage:  64.2% of statements in consensus/istanbul/uptime
coverage:  51.8% of statements in consensus/istanbul/validator
coverage:  79.2% of statements in consensus/istanbul/validator/random

[github-actions[bot]]

Test failures:
TestTransactionIndices: core blockchain_test.go:1946: Oldest indexded block mismatch, want 100, have 67
This test report was produced by the test-summary action.  Made with ❤️ in Cambridge.

[palango]

Codecov submission currently only works on master, so this doesn't change that.