Allow `batch-mark-files-as-viewed`'s "toggle all with alt-click" on checkbox label #4155

In #4016, @yakov116 added the "toggle all with alt-click" to batch-mark-files-as-viewed, but it works only if you click directly on the checkbox (.js-reviewed-checkbox).

It'd be nice if it would also work when clicking on the whole label (.js-reviewed-toggle). A click or alt-click does trigger this one checkbox to change, but not all others.