.wrap {
max-width: 100%;
}
@media screen and (min-width: 48em) {
.wrap {
max-width: 100%;
}
}
.page.page-one-column:not(.twentyseventeen-front-page) #primary {
max-width: 100%;
}
@media screen and (min-width: 30em) {
.page-one-column .panel-content .wrap {
max-width: 100%;
}
}
You can adjust the 100%
values. Set these to 90% for example for a 90% main content width.