Batch id link for document restoration does not have any text

This issue was first found with automated WCAG tests (build #645 for example):

WCAG fails in the test class [org.xwiki.administration.test.ui.AllIT]:
__________
Validation in the test method [createAndDeleteUser]
Check for [org.xwiki.test.ui.po.ViewPage] at http://xwikiweb:8080/xwiki/bin/view/XWiki/createAndDeleteUser.
Found [1] items

1: Links must have discernible text
Description: Ensures links have discernible text
Help URL: https://dequeuniversity.com/rules/axe/4.9/link-name?application=axeAPI
Help: Links must have discernible text
Impact: serious
Tags: cat.name-role-value, wcag2a, wcag244, wcag412, section508, section508.22.a, TTv5, TT6.a, EN-301-549, EN-9.2.4.4, EN-9.4.1.2, ACT

HTML element:
<a href="/xwiki/bin/undelete/XWiki/createAndDeleteUser?id=49&showBatch=true"></a>
Selector: [td:nth-child(3) > a]
Fix all of the following:
Element is in tab order and does not have accessible text

Fix any of the following:
Element does not have text that is visible to screen readers
aria-label attribute does not exist or is empty
aria-labelledby attribute does not exist, references elements that do not exist or references elements that are empty
Element has no title attribute

__________
Validation in the test method [createAndDeleteUser]
Check for [org.xwiki.test.ui.po.DeletePageOutcomePage] at http://xwikiweb:8080/xwiki/bin/view/XWiki/createAndDeleteUser.
Found [1] items

1: Links must have discernible text
Description: Ensures links have discernible text
Help URL: https://dequeuniversity.com/rules/axe/4.9/link-name?application=axeAPI
Help: Links must have discernible text
Impact: serious
Tags: cat.name-role-value, wcag2a, wcag244, wcag412, section508, section508.22.a, TTv5, TT6.a, EN-301-549, EN-9.2.4.4, EN-9.4.1.2, ACT

HTML element:
<a href="/xwiki/bin/undelete/XWiki/createAndDeleteUser?id=49&showBatch=true"></a>
Selector: [td:nth-child(3) > a]
Fix all of the following:
Element is in tab order and does not have accessible text

Fix any of the following:
Element does not have text that is visible to screen readers
aria-label attribute does not exist or is empty
aria-labelledby attribute does not exist, references elements that do not exist or references elements that are empty
Element has no title attribute

==> expected: <false> but was: <true>

This fail highlights that in some cases, we have links that do not have any text. In most cases, we cannot see those links, so it does not matter much. However it would be an issue for screen readers