fix: fix Less linter warnings in adminhtml

[DanielRuf]

Description

This fixes a few findings of the linter in VisualStudio Code.

Fixed Issues (if relevant)

1. ...
2. ...

Manual testing scenarios

1. ...
2. ...

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[magento-engcom-team]

Hi @DanielRuf. Thank you for your contribution
Here is some useful tips how you can test your changes using Magento test environment.
Add the comment under your pull request to deploy test or vanilla Magento instance:

• @magento-engcom-team give me test instance - deploy test instance based on PR changes
• @magento-engcom-team give me {$VERSION} instance - deploy vanilla Magento instance

For more details, please, review the Magento Contributor Assistant documentation

[VladimirZaets]

Are you sure that we can change display inline-block to block? It can break UI.

[DanielRuf]

Due to float it is always handled as block.

See https://codepen.io/DanielRuf/pen/bjxgwm?editors=1100

[DanielRuf]

https://developer.mozilla.org/en-US/docs/Web/CSS/float

As float implies the use of the block layout, it modifies the computed value of the display values, in some cases:

specified	computed
inline	block
inline-block	block
inline-table	table
table-row	block
table-row-group	block
table-column	block
table-column-group	block
table-cell	block
table-caption	block
table-header-group	block
table-footer-group	block
flex	flex, but float has no effect on such elements
inline-flex	inline-flex, but float has no effect on such elements
other	unchanged

[DanielRuf]

@magento-engcom-team give me test instance

[magento-engcom-team]

Hi @DanielRuf. Thank you for your request. I'm working on Magento instance for you

[magento-engcom-team]

Hi @DanielRuf, here is your new Magento instance.
Admin access: https://pr-17343.engcom.dev.magento.com/admin
Login: admin Password: 123123q

[VladimirZaets]

@DanielRuf ok, thanks

[magento-engcom-team]

Hi @DanielRuf. Thank you for your contribution.
We will aim to release these changes as part of 2.3.0.
Please check the release notes for final confirmation.