This changeset adds `text-decoration-thickness: 2px;` to all underlined link to ensure that underline thickness stay consistent across browsers. This fixes an issue where the underline style on links using the Hoefler Text font was too thin in Firefox.
Props allancole, sabernhardt, danfarrow, audrasjb, neychok, multidots1896, maartenj.
Fixes#45925.
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