Fix CSS variable checker breaking build

For a while now a false negative would occur with the css variable
checker (which goal is to ensure we don't reference undefined css
variables). Turns out, in omni-search.css one of the
var(--font-size-medium), even though it looked correct and with the
right characters would not pass a JavaScript equality check thus
resulting in the false negative. I just rewrote that line to fix the
problem. Even the diff says that they are different, but offer no
indication of what is different. 🤷

Author: hojberg

src/css/unison-share/omni-search.css

@@ -376,7 +376,7 @@
 
     & .icon {
       color: var(--u-color_icon_subdued);
-      font-size: var(--font–size-medium);
+      font-size: var(--font-size-medium);
     }
   }
 

src/css/unison-share/page/code-page.css

@@ -7,7 +7,9 @@
    --readable-column-width-medium originally is 43 and we're adding 2rem;
    * */
   --readable-column-width-medium_original: 43rem;
-  --readable-column-width-medium: calc(var(--readable-column-width-medium_original) + 2rem);
+  --readable-column-width-medium: calc(
+    var(--readable-column-width-medium_original) + 2rem
+  );
 }
 
 .code-page .sidebar .namespace-header {