Revert "Add theme URL param and adjust cpd theme based on it."

This reverts commit f613b17824.

src/Header.module.css

@@ -33,7 +33,6 @@ limitations under the License.
 }
 
 .headerLogo {
-  color: var(--cpd-color-text-primary);
   display: none;
   align-items: center;
   text-decoration: none;