Update actions/checkout action to v3

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
actions/checkout	action	major	v2 -> v3

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Release Notes

actions/checkout

### [`v3`](https://togithub.com/actions/checkout/compare/v2...v3) [Compare Source](https://togithub.com/actions/checkout/compare/v2...v3)

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[codecov[bot]]

Codecov Report

Merging #5 (12e4e22) into master (1909ed5) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master       #5   +/-   ##
=======================================
  Coverage   96.92%   96.92%           
=======================================
  Files           1        1           
  Lines          65       65           
  Branches        9        9           
=======================================
  Hits           63       63           
  Misses          2        2           

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