Use codecov uploader in favor of bash uploader for coverage reports

[umesh-timalsina]

PR Summary:

https://docs.codecov.com/docs/about-the-codecov-bash-uploader#deprecation-notice-and-schedule

Suggests that the bash uploader we use will be deprecated soon. This PR uses the recommended codecov uploader to upload coverage reports.

PR Checklist

---

• [ ] Includes appropriate unit test(s): N/A
• [ ] Appropriate docstring(s) are added/updated: N/A
• [ ] Code is (approximately) PEP8 compliant: N/A
• [ ] Issue(s) raised/addressed? : N/A

[codecov[bot]]

Codecov Report

Merging #468 (91f327f) into master (1f91c3e) will not change coverage. The diff coverage is 66.66%.

@@           Coverage Diff           @@
##           master     #468   +/-   ##
=======================================
  Coverage   73.87%   73.87%           
=======================================
  Files          17       17           
  Lines        1849     1849           
=======================================
  Hits         1366     1366           
  Misses        483      483