We are replacing `--in-content-box-background-odd` variable with new `--table-row-background-color-alternate` design token (see patch [[ https://phabricator.services.mozilla.com/D231953 | D231953 ]]). But the new token isn't semantically correct for the `private-window-message` and `tab-content` elements, so I am replacing it with `--in-content-box-info-background` variable. Before: {F11341526} After: {F11341531} Differential Revision: https://phabricator.services.mozilla.com/D233462