Bump to newer codecov action

[sliverc]

Description of the Change

Codecov Action v1 is deprecated and will be removed, therefore updating to newest runner v2. See here for more details.

Checklist

• PR only contains one change (considered splitting up PR)
• unit-test added
• documentation updated
• CHANGELOG.md updated (only for user relevant changes)
• author name in AUTHORS

[codecov]

Codecov Report

Merging #996 (8524467) into master (06c3ef4) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #996   +/-   ##
=======================================
  Coverage   96.84%   96.84%           
=======================================
  Files          65       65           
  Lines        3933     3933           
=======================================
  Hits         3809     3809           
  Misses        124      124           

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