[M116][PriceInsights] Add UI Polishes

* Add underline to folder name link.
* Use different color for toggle annotation texts.

(cherry picked from commit 6ef2c00)

Bug: 1462744, 1456420
Change-Id: I1793c61b2d6e38e6806b24f5c6d54b5e3e1789b1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4671011
Reviewed-by: John Lee <johntlee@chromium.org>
Commit-Queue: Yue Zhang <yuezhanggg@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#1167599}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4670274
Cr-Commit-Position: refs/branch-heads/5845@{#404}
Cr-Branched-From: 5a5dff6-refs/heads/main@{#1160321}

chrome/browser/resources/side_panel/commerce/price_tracking_section.html

@@ -15,10 +15,10 @@
 
   #toggleAnnotationButton {
     color: var(--cr-link-color);
-    text-decoration: none;
   }
 
   #toggleAnnotation {
+    color: var(--cr-secondary-text-color);
     display: inline;
     font-size: 11px;
     overflow: hidden;