Use link-color in the Choose Tryjobs panel

Using link-color makes links more readable in dark mode.

Bug: 1284762
Change-Id: I34ec6b7e803f4be37fe01cdc4665968c2efc9257
Reviewed-on: https://chromium-review.googlesource.com/c/infra/gerrit-plugins/buildbucket/+/3368665
Auto-Submit: Gavin Mak <gavinmak@google.com>
Reviewed-by: Aravind Vasudevan <aravindvasudev@google.com>
Commit-Queue: Gavin Mak <gavinmak@google.com>

src/main/resources/static/cr-tryjob-picker_html.js

diff --git a/src/main/resources/static/cr-tryjob-picker_html.js b/src/main/resources/static/cr-tryjob-picker_html.js
index e7fcc52..2853637 100644
--- a/src/main/resources/static/cr-tryjob-picker_html.js
+++ b/src/main/resources/static/cr-tryjob-picker_html.js
@@ -13,6 +13,9 @@
     footer {
       padding: 1em;
     }
+    a {
+      color: var(--link-color);
+    }
     header {
       align-items: center;
       border-bottom: 1px solid #ddd;