I think you have missed a closing bracket somewhere. Please try adding a curly brace before the code snippet like this
}
.product-form {
margin-bottom: 0 !important;
}
.product__info-container .list.list-payment {
/* You can adjust this value according to your preference */
margin-bottom: 100px;
}
or pasting this code snippet into theme.liquid file, right before the closing head tag
Hope this will help you resolve your issue!