updates in Username

tgbotapi.core/src/commonTest/kotlin/dev/inmo/tgbotapi/types/ChatIdentifierTests.kt

@@ -35,9 +35,7 @@ class ChatIdentifierTests {
     fun `Cast_from_String_to_Username_is_working_correctly`() {
         assertEquals(testUsername, testUsername.toUsername().full)
 
-        assertFails("Username creating must fail when trying to create from string which is not starting from @ symbol") {
-            testUsername.replace("@", "").toUsername().full
-        }
+        assertEquals(testUsername, testUsername.replace("@", "").toUsername().full)
     }
 
     @Serializable