fix: incorrect zoom out factor when using using wheel

[kurkle]

fixes: #767

[github-actions[bot]]

Size Change: +397 B (+1.97%)

Total Size: 20.5 kB

Filename	Size	Change
dist/chartjs-plugin-zoom.esm.js	7.43 kB	+148 B (+2.03%)
dist/chartjs-plugin-zoom.js	7.58 kB	+142 B (+1.91%)
dist/chartjs-plugin-zoom.min.js	5.5 kB	+107 B (+1.98%)

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