Grid: Add button styling fix

[BatJan]

Prerequisites

• I have added steps to test this contribution in the description below

Description

With the current release of version 8.16 I noticed the "Add button" in the grid was no longer a perfect square after the icon was converted to using the <umb-icon> directive. That's addressed with a few tweaks to the .iconBox class in this PR.

Furthermore some unused classes and uneeded CSS properties have been removed 😃

Before

After

[bjarnef]

Another thing that is redundant is setting border-color here and then override it right after on next line 😅

Umbraco-CMS/src/Umbraco.Web.UI.Client/src/less/components/umb-grid.less

Lines 601 to 602 in 4eed7d6

	border-color: @gray-7 @gray-7 @gray-6;
	border-color: rgba(0,0,0,0.1) rgba(0,0,0,0.1) rgba(0,0,0,0.25);

Although some very old browsers didn't support rgba in CSS, it probably isn't relevant anymore. https://caniuse.com/?search=rgba

[BatJan]

@bjarnef Ah yes, removed that as well now 👍🏻 All the browsers that Umbraco aim to support has rgba() support for a long time so no worries about that one 😃

[umbrabot]

Hi there @BatJan, thank you for this contribution! 👍

While we wait for one of the Core Collaborators team to have a look at your work, we wanted to let you know about that we have a checklist for some of the things we will consider during review:

• It's clear what problem this is solving, there's a connected issue or a description of what the changes do and how to test them
• The automated tests all pass (see "Checks" tab on this PR)
• The level of security for this contribution is the same or improved
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• Avoids creating breaking changes; note that behavioral changes might also be perceived as breaking
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[nul800sebastiaan]

@BatJan Could package developers be using .umb-grid .iconBox i? Cleaning up is great but we have to consider who else is using our styling. :-)

[BatJan]

@nul800sebastiaan Good catch! Reverted now 👍🏻

[nathanwoulfe]

Looks good to me, thanks @BatJan

[nathanwoulfe]

@nul800sebastiaan I've labelled this for 8.17 - is it possible to cherry pick for that release or will it need to wait? Not a big issue, but would be good to resolve.

[nathanwoulfe]

Failed test isn't related to this change

[nul800sebastiaan]

Cherry picked for 8.17 in e269d1b