Align decrediton's global box-sizing property with pi-ui.

[amass01]

This gets rid of a styling hack which was used to resolve a global styling conflict between pi-ui and
decrediton.

Before this commit:

/* TODO: delete box-sizing: content-box;
// I added this ugly `:not` workaround to be able to skip pi-ui's classes
// which are prefixed with 'styles_'.
// Ideally we should use `* { box-sizing: inherit; } and html { box-sizing: border-box }`(already done in pi-ui)
// we shouldn't override it in a global level - we should take care of this while migrating this file to a css module.*/
*:not([class^="styles_"]),
*:not([class^="styles_"])::before,
*:not([class^="styles_"])::after {
  box-sizing: content-box;
}

[class^="styles_"] > * {
  box-sizing: inherit;
}

As mentioned in the code comment above; before this diff decrediton's needed box-sizing: content-box; which conflicted with pi-ui's which defines * { box-sizing: inherit; } and html { box-sizing: border-box }.

After ditching box-sizing: content-box; I needed to tweak width/height property of many parts of decrediton.

[alexlyp]

Not sure if it was introduced in this PR, but seeing a misalignment in the Extended PubKey area in Account Details

[alexlyp]

Yah confirmed that it was introduced in this PR.

[amass01]

@alexlyp good catch, updating it.

[amass01]

@alexlyp updated 👍

[alexlyp]

tACK