I have tried these methods

button::after{
  border: none;
}
.loginBut::after{
  border: 0;
}

button[class="loginBut"]::after {
  border: 0;
}
.button-hover {
  border: 0;
}

.button-hover::after {
  border: 0;
}

however, whether Mini Program updates button or not,
hopes that Tencent can accept different aesthetics.

er, I"m sorry, I tried but this morning. I really don"t have border, but I don"t like it. Last night, it was done by this bug for a long time.

git code rollback, huh! My problem is that button added plain= "true" this; (