Rollup merge of #110307 - est31:beta_nominated_unauthenticated, r=Mark-Simulacrum

Allow everyone to set the beta-nominated label

It is allowed both in cargo and clippy's triagebot.toml, and nomination does not automatically mean that the PR will be backported.

Author: JohnTitor

triagebot.toml

@@ -11,6 +11,7 @@ allow-unauthenticated = [
     "S-*",
     "T-*",
     "WG-*",
+    "beta-nominated",
     "const-hack",
     "llvm-main",
     "needs-fcp",