Dashboard banner fix.

[YegorSan]

@vbaranov
Hello Victor.
I've fixed issue with dashboard-banner-chart-legend bottom items incorrect rendering.

Bug Fixes

Changed display value for dashboard-banner-chart-legend class from flex to grid. Changed right padding for dashboard-banner-chart-legend-item. Chart legend Items should be rendered as it's expected now.

Checklist for your PR

• I added an entry to CHANGELOG.md with this PR
• If I added new functionality, I added tests covering it.
• If I fixed a bug, I added a regression test to prevent the bug from silently reappearing again.
• I checked whether I should update the docs and did so if necessary
• If I added/changed/removed ENV var, I should update the list of env vars in https://github.com/poanetwork/blockscout/blob/master/docs/env-variables.md to reflect changes in the table here https://poanetwork.github.io/blockscout/#/env-variables?id=blockscout-env-variables. I've set master in the Version column.
• If I add new indices into DB, I checked, that they don't redundant with PGHero or other tools