Website: update cta-button mixin hover state (#43717)

Changes:
- Added hover styles to the cta-button mixin.

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

## Summary by CodeRabbit

* **Style**
* Call-to-action buttons now display white text without underline on
hover.

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

website/assets/styles/mixins-and-variables/buttons.less

@@ -98,6 +98,10 @@
   align-items: center;
   font-weight: 700;
   border-radius: 8px;
+  &:hover {
+    color: #FFF;
+    text-decoration: none;
+  }
   &:before {
     background: linear-gradient(180deg, rgba(255, 255, 255, 0.2) 0%, rgba(255, 255, 255, 0) 100%);
     opacity: 1;