Underline inline links on the change viewer

Highlighted first by automated WCAG tests.

Example of a violation report:

Validation in the test method [diffWithDeletedAttachments]
Check for [org.xwiki.test.ui.po.ComparePage] at http://xwikiweb:8080/xwiki/bin/view/NestedAttachmentIT/diffWithDeletedAttachments/?viewer=changes&rev1=1.1&rev2=2.1&.
Found [1] items

1: Links must be distinguishable without relying on color
Description: Ensure links are distinguished from surrounding text in a way that does not rely on color
Help URL: https://dequeuniversity.com/rules/axe/4.8/link-in-text-block?application=axeAPI
Help: Links must be distinguishable without relying on color
Impact: serious
Tags: cat.color, wcag2a, wcag141, TTv5, TT13.a, EN-301-549, EN-9.1.4.1

HTML element:
<a href="/xwiki/bin/view/NestedAttachmentIT/diffWithDeletedAttachments/?rev=1.1">1.1</a>
Selector: [#changes-info-box-from > .changes-info-title > .changes-version > a:nth-child(1)]
Fix any of the following:
The link has insufficient color contrast of 1.41:1 with the surrounding text. (Minimum contrast is 3:1, link text: #2f70a7, surrounding text: #555555)
The link has no styling (such as underline) to distinguish it from the surrounding text

HTML element:
<a href="/xwiki/bin/view/XWiki/User1">User1</a>
Selector: changes-info-box-from > .changes-info-content > .wikilink > a[href$="User1"]
Fix any of the following:
The link has insufficient color contrast of 1.41:1 with the surrounding text. (Minimum contrast is 3:1, link text: #2f70a7, surrounding text: #555555)
The link has no styling (such as underline) to distinguish it from the surrounding text