Portal: remove underlines from links in changelog page (#8148)

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## PR-Codex overview
This PR focuses on updating the styles for links within the `changelog-page` in the `styles.css` file, specifically removing certain text decoration properties.

### Detailed summary
- Removed the text decoration properties (`text-decoration`, `text-decoration-color`, `text-decoration-style`, `text-underline-offset`, `transition`) from the `.changelog-page a` selector.

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<!-- This is an auto-generated comment: release notes by coderabbit.ai -->

## Summary by CodeRabbit

* **Style**
  * Updated link appearance on the changelog page for consistency with global styles. Regular links no longer use custom underlines or color transitions, resulting in a cleaner look and improved readability. Headings remain without underlines, and hover behavior is unchanged. Users should notice a more consistent visual experience across the page without functional changes.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: MananTank

apps/portal/src/app/changelog/[slug]/styles.css

@@ -2,15 +2,6 @@
   display: none;
 }
 
-.changelog-page a {
-  text-decoration: underline;
-  text-decoration-color: hsl(var(--muted-foreground));
-  text-decoration-style: dotted;
-  color: hsl(var(--foreground));
-  text-underline-offset: 5px;
-  transition: color 200ms ease;
-}
-
 .changelog-page h2 a {
   text-decoration: none;
 }