Rollup merge of rust-lang#90563 - joshtriplett:rustbot-allow-labels, …

…r=Mark-Simulacrum

rustbot allow labels

`relnotes` was inspired by rust-lang#90521 , and by the various `must_use` PRs; in all of those cases, the submitter of the PR could know that `relnotes` applied, but couldn't apply it themselves.

For `needs-fcp`, I think people should be able to help triage by observing that a change needs an FCP before we can apply it.

triagebot.toml

@@ -2,6 +2,8 @@
 allow-unauthenticated = [
     "C-*", "A-*", "E-*", "NLL-*", "O-*", "S-*", "T-*", "WG-*", "F-*",
     "D-*",
+    "needs-fcp",
+    "relnotes",
     "requires-nightly",
     "regression-*",
     "perf-*",