Clarify authz comments - #11028

control: job assigned to worker 01KZF1QDJTYFD8RFPC56Z3P32S [factory aws, i-083d845a3e54c26a3] (queued for 1 m 1 s)
...
task: starting task 0: "setup"
task: process exited: duration 4141 ms, exit code 0
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task: starting task 1: "rust-toolchain"
task: process exited: duration 17285 ms, exit code 0
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task: starting task 2: "authentication"
task: process exited: duration 18 ms, exit code 0
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task: starting task 3: "clone repository"
task: process exited: duration 11288 ms, exit code 0
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task: starting task 4: "build"
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| a out/probe.tar.gz 3037K
| a out/propolis-server.tar.gz 34642K
| a out/pumpkind-gz.tar 26647K
| a out/switch-softnpu.tar.gz 498977K
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| real     1:29.217296767
| user     1:26.232188227
| sys         4.962471484
| trap        0.007438848
| tflt        0.000000000
| dflt        0.000000000
| kflt        0.000000000
| lock        0.000000000
| slp      1:26.081784696
| lat         1.146192738
| stop        0.000202590
task: process exited: duration 1053054 ms, exit code 0
|W| found 1 output files
|W| uploading: /work/package.tar.gz (2759768987 bytes)
|W| uploaded: /work/package.tar.gz