css: Replace "night-mode-block" with "dark-theme-block".

Author: sahil839

postcss.config.js

@@ -11,7 +11,7 @@ module.exports = ({file}) => ({
             // the flatpickr dark theme. We do this because flatpickr themes
             // are not scoped. See https://github.com/flatpickr/flatpickr/issues/2168.
             require("postcss-import")({
-                plugins: [require("postcss-prefixwrap")("%night-mode-block")],
+                plugins: [require("postcss-prefixwrap")("%dark-theme-block")],
             }),
         require("postcss-nested"),
         require("postcss-extend-rule"),

static/styles/dark_theme.css

@@ -4,7 +4,7 @@ body.dark-theme {
     /* the following block(s) are generated by the import statements.
        See postcss.config.js for details.
      */
-    @extend %night-mode-block;
+    @extend %dark-theme-block;
 
     background-color: hsl(212, 28%, 18%);
     color: hsl(236, 33%, 90%);