chore(pages): remove MacPorts install channel (#1334)

Drop the MacPorts option from the landing page install switcher and
the documentation site, since it is no longer a recommended way to
install ocr.

- Remove the macports entry and icon import from INSTALL_CHANNELS
- Delete the macports.svg icon and the hero.installMacPorts label
  from all five locale tables
- Remove the MacPorts section from every installation.md and adjust
  the install-method count from six to five
- Switch the overflow-channel test to the Windows channel