Update Medium articles promo on homepage for 6.4

[edonehoo]

Let's promo https://medium.com/patternfly/open-source-is-a-two-way-street-71c31f6c8384 & anything else that is published around release

[edonehoo]

there are no more blogs to promo before the release. We'll have more published during the quarter and could maybe just one-off update org?