MM-41211: Replaces SessionLength*InDays with SessionLength*InHours. (#19838)

* MM-41211: Replaces SessionLength[Web|Mobile|SSO]InDays with SessionLength[Web|Mobile|SSO]InHours.

* MM-41211: Clear the value of the old config settings.

manualtesting/manual_testing.go

@@ -143,7 +143,7 @@ func manualTest(c *web.Context, w http.ResponseWriter, r *http.Request) {
 			Name:     model.SessionCookieToken,
 			Value:    client.AuthToken,
 			Path:     "/",
-			MaxAge:   *c.App.Config().ServiceSettings.SessionLengthWebInDays * 60 * 60 * 24,
+			MaxAge:   *c.App.Config().ServiceSettings.SessionLengthWebInHours * 60 * 60,
 			HttpOnly: true,
 		}
 		http.SetCookie(w, sessionCookie)