Update Mage

[philippgille]

From 1.13 to 1.15. See their release notes:

• https://github.com/magefile/mage/releases/tag/v1.14.0
• https://github.com/magefile/mage/releases/tag/v1.15.0

[codecov-commenter]

Codecov Report

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

Comparison is base (504729c) 65.26% compared to head (7eb9f95) 65.26%.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #148 +/- ## ======================================= Coverage 65.26% 65.26% ======================================= Files 25 25 Lines 2096 2096 ======================================= Hits 1368 1368 Misses 601 601 Partials 127 127 ```

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