please update src/stage0.json for beta channel

[stefson]

hi,

beta channel still uses beta rust-std+rustc to compile the branch, as per src/stage0:

  "compiler": {
    "date": "2023-08-22",
    "version": "beta"
  },

Can you please update this to stable-1.73.0? I run my own custom target, and am unable to beta test for rust-1.74.0 at the moment.

thanks

[ehuss]

This will be completed by #117005.

[ChrisDenton]

closing this as per the above comment