Broken Darwin downloads

[mxschmitt]

Repro:

1. Navigate to https://www.electronjs.org/fiddle
2. Click on Download on darwin-arm64

It ends up using

https://github.com/electron/fiddle/releases/download/0.34.5/Electron.Fiddle-darwin-arm64-0.34.5.zip

which is a 404 but it should use:

https://github.com/electron/fiddle/releases/download/v0.34.5/Electron.Fiddle-darwin-arm64-0.34.5.zip

(missing v version prefix)

[mxschmitt]

Probably caused by electron/website@c41589b.

cc @dsanders11

[dsanders11]

Thanks!