Remove CSS replaced by sphinx-design

cf. matplotlib/matplotlib#23169

Author: QuLogic

mpl_sphinx_theme/static/css/style.css

@@ -45,29 +45,6 @@ html[data-theme="dark"] {
   font-size: 1.0em;
 }
 
-
-.mpl-button {
-  background: #11557C;
-  font-weight: normal;
-  display: inline-block;
-  padding: 0 1em;
-  line-height: 2.8;
-  font-size: 16px;
-  text-align: center;
-  cursor: pointer;
-  color: #fff;
-  text-decoration: none;
-  border-radius: 6px;
-  z-index: 1;
-  transition: background .25s ease;
-}
-
-.mpl-button:hover, .mpl-button:active, .mpl-button:focus {
-  background: #003c63;
-  outline-color: #003c63;
-}
-
-
 /* Hide red ¶ between the thumbnail and caption in gallery
 
 Due the way that sphinx-gallery floats its captions the perma-link
@@ -97,22 +74,3 @@ table.property-table td {
 .sidebar-cheatsheets, .sidebar-donate {
   margin: 2.75rem 0;
 }
-
-.sidebar-donate .mpl-button {
-  /* fix width to width of cheatsheet */
-  width: 210px;
-}
-
-/* Two columns for install code blocks */
-div.twocol {
-  padding-left: 0;
-  padding-right: 0;
-  display: flex;
-  gap: 20px;
-}
-
-div.twocol > div {
-  flex-grow: 1;
-  padding: 0;
-  margin: 0;
-}