Fix default inline code color

To match the rest of the theme.

Signed-off-by: Kévin Commaille <zecakeh@tedomum.fr>

assets/scss/_variables_project.scss

@@ -18,6 +18,7 @@ $primary: #FFF;
 $secondary: #0098D4;
 $dark: #333;
 $gray-100: #FBFBFB;
+$code-color: #005b7f;
 
 $secondary-background: #E5F5FB;
 $secondary-lighter-background: #F4FAFC;