Update main.yml

[logsdail]

Updated CodeCov to v4 (recommended)

[logsdail]

For record, updates taken from here: https://github.com/marketplace/actions/codecov with additional ideas/reading taken from https://github.com/codecov/codecov-action/issues/557

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 88.23%. Comparing base (4174d1e) to head (439fcd2).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #157 +/- ## ======================================= Coverage 88.23% 88.23% ======================================= Files 80 80 Lines 3265 3265 ======================================= Hits 2881 2881 Misses 384 384 ``` | [Flag](https://app.codecov.io/gh/logsdail/carmm/pull/157/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Andrew+Logsdail) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/logsdail/carmm/pull/157/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Andrew+Logsdail) | `88.23% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Andrew+Logsdail#carryforward-flags-in-the-pull-request-comment) to find out more.

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[AkashHiregange]

The update to v4 works as seen in my pull request #155. Hence merging this into main.