input/tidal: pass std::string by value

Don't keep any references to the owner, as the handler method may
delete the owner.

src/input/plugins/TidalSessionManager.hxx

@@ -158,7 +158,7 @@ private:
 	}
 
 	/* virtual methods from TidalLoginHandler */
-	void OnTidalLoginSuccess(std::string &&session) noexcept override;
+	void OnTidalLoginSuccess(std::string session) noexcept override;
 	void OnTidalLoginError(std::exception_ptr error) noexcept override;
 };