Rollup merge of #60891 - jonas-schievink:triagebot-claim, r=Mark-Simulacrum

Allow claiming issues with triagebot

Not sure if this was intentionally left out, but it can probably be enabled now that rust-lang/triagebot#3 is fixed (assuming that the deployed commit is recent enough). People have tried to use it already (#60622 (comment)).

r? @Mark-Simulacrum

Author: Manishearth

triagebot.toml

@@ -4,3 +4,5 @@ allow-unauthenticated = [
     # I-* without I-nominated
     "I-compilemem", "I-compiletime", "I-crash", "I-hang", "I-ICE", "I-slow",
 ]
+
+[assign]