Release channel support - Make Release channel the default download on March 4

[coreycb]

We are planning to switch the default download to the Release channel on March 4th, 2025 (136.0 release). This work will need to be timed to be published on the website the same day as the 136.0 release.

Can we update https://www.thunderbird.net/en-US/thunderbird/all/ to default to "Thunderbird Release" channel on March 4th?

Can we also add some text stating the Release channel will be downloaded at https://www.thunderbird.net/en-US/ when the Download button is clicked? An example of the concern here is that users are sometimes asked on sumo to download Thunderbird again, and with the default download on this page changing without users knowing that it is no longer downloading the ESR channel, they may end up on Release unexpectedly.