Fix build issue

Author: AntsyLich

library/src/main/java/eu/kanade/tachiyomi/source/online/HttpSource.kt

@@ -245,15 +245,15 @@ abstract class HttpSource : CatalogueSource {
      *
      * @param url the full url to the chapter.
      */
-    fun SChapter.setUrlWithoutDomain(url: String) = throw Exception("Stub!")
+    fun SChapter.setUrlWithoutDomain(url: String): Unit = throw Exception("Stub!")
 
     /**
      * Assigns the url of the manga without the scheme and domain. It saves some redundancy from
      * database and the urls could still work after a domain change.
      *
      * @param url the full url to the manga.
      */
-    fun SManga.setUrlWithoutDomain(url: String) = throw Exception("Stub!")
+    fun SManga.setUrlWithoutDomain(url: String): Unit = throw Exception("Stub!")
 
     /**
      * Returns the url of the given string without the scheme and domain.