Repro #20488: Trend visualization percentage rounding decimals (#20492)

* Add repro for #20488

* Update frontend/test/metabase/scenarios/visualizations/smartscalar-trend.cy.spec.js

Co-authored-by: flamber <1447303+flamber@users.noreply.github.com>

* Update number formatting

Co-authored-by: flamber <1447303+flamber@users.noreply.github.com>