minor #1344 [Site] Minor fixes (smnandre)

This PR was squashed before being merged into the 2.x branch.

Discussion
----------

[Site] Minor fixes

Remove 40kb glitchy background under hero
(it was visible only on the homepage, in dark mode... and see pictures)

Before light:
![before-light](https://github.com/symfony/ux/assets/1359581/71bf4bc4-5a22-499a-ad9d-d23f2e75f11f)

Before dark:
![before](https://github.com/symfony/ux/assets/1359581/850a3441-f77f-4b21-a8c5-30cf8e96dc94)

After dark
![after](https://github.com/symfony/ux/assets/1359581/4fd30d5c-0503-41c5-8a34-2d919dafe309)

Also:
* fix package box titles
* improve copy button colors

Commits
-------

fa5f84c [Site] Minor fixes

ux.symfony.com/assets/styles/components/_PackageBox.scss

@@ -118,12 +118,8 @@
   font-size: 28px !important;
   line-height: 32px !important;
   letter-spacing: -1px;
-  color: #0A0A0A;
+  color: var(--bs-body-color);
   text-decoration: none;
-
-  [data-bs-theme="dark"] & {
-    filter: invert(1);
-  }
 }
 
 .PackageBox_link {

ux.symfony.com/assets/styles/components/_Terminal.scss

@@ -111,16 +111,13 @@
         color: $n-200;
         background: none;
     }
-
     .btn-copy {
-        background-color: $n-700;
         color: $n-200;
-        &:active {
-            background-color: $n-700;
-            color: $n-200;
-        }
+        background: none;
+        transition: all 250ms ease-in-out;
         &:hover {
-            background-color: $n-600;
+            color: $n-100;
+            background-color: $n-800;
         }
     }
     .btn-link:hover {

ux.symfony.com/assets/styles/sections/_hero.scss

@@ -10,20 +10,7 @@
 }
 
 .hero-background {
-  background: url(../images/background_homepage.png);
-  background-size: cover;
   padding-block-start: 4rem;
-
-  &::after {
-    content: "";
-    display: block;
-    position: absolute;
-    background: #d75b5b00;
-    width: 100%;
-    margin-block-start: -1.5rem;
-    backdrop-filter: blur(1rem);
-    height: 3rem;
-  }
 }
 
 .hero-sub-text {