remove dark mode from waterfall demo

The main Zola theme doesn't have dark mode, so having dark mode in
the waterfall demo UI looks bad, since the rest of the site is in
light mode.

Signed-off-by: Daniel Estévez <[email protected]>

Author: daniestevez

content/waterfall_demo.md

@@ -37,31 +37,6 @@ main .toc {
     --stopping-color: #dd9;
 }
 
-@media (prefers-color-scheme: dark) {
-    /* Dark mode */
-    :root {
-        --background-color: black;
-        --text-color: white;
-        --line-color: white;
-
-        --focus-outline-color: rgba(208, 208, 255, 0.5);
-
-        --input-bg-color: #222;
-        --input-highlight-color: #227;
-        --input-bg-invalid-color: #ffb0b0;
-
-        --button-color: #444;
-        --button-highlight-color: #777;
-
-        /* Record button */
-        --record-color: #7b7;
-        --record-highlight-color: #9d9;
-        --stop-color: #b77;
-        --stop-highlight-color: #d99;
-        --stopping-color: #bb7;
-    }
-}
-
 #waterfall {
     touch-action: none;
     width: 100%;