…nal/kokoro/discogen (#2911)

Bumps [golang.org/x/crypto](https://togithub.com/golang/crypto) from 0.21.0 to 0.31.0.
<details>
<summary>Commits</summary>
<ul>
<li><a href="https://togithub.com/golang/crypto/commit/b4f1988a35dee11ec3e05d6bf3e90b695fbd8909"><code>b4f1988</code></a> ssh: make the public key cache a 1-entry FIFO cache</li>
<li><a href="https://togithub.com/golang/crypto/commit/7042ebcbe097f305ba3a93f9a22b4befa4b83d29"><code>7042ebc</code></a> openpgp/clearsign: just use rand.Reader in tests</li>
<li><a href="https://togithub.com/golang/crypto/commit/3e90321ac7bcee3d924ed63ed3ad97be2079cb56"><code>3e90321</code></a> go.mod: update golang.org/x dependencies</li>
<li><a href="https://togithub.com/golang/crypto/commit/8c4e668694ccbaa1be4785da7e7a40f2ef93152b"><code>8c4e668</code></a> x509roots/fallback: update bundle</li>
<li><a href="https://togithub.com/golang/crypto/commit/6018723c74059e3b91c84268b212c2f6cdab1f64"><code>6018723</code></a> go.mod: update golang.org/x dependencies</li>
<li><a href="https://togithub.com/golang/crypto/commit/71ed71b4faf97caafd1863fed003e9ac311f10ee"><code>71ed71b</code></a> README: don't recommend go get</li>
<li><a href="https://togithub.com/golang/crypto/commit/750a45fe5e473d5afa193e9088f3d135e64eca26"><code>750a45f</code></a> sha3: add MarshalBinary, AppendBinary, and UnmarshalBinary</li>
<li><a href="https://togithub.com/golang/crypto/commit/36b172546bd03a74c79e109ec84c599b672ea9e4"><code>36b1725</code></a> sha3: avoid trailing permutation</li>
<li><a href="https://togithub.com/golang/crypto/commit/80ea76eb17c0c52f5d5d04e833d6aeb6b062d81d"><code>80ea76e</code></a> sha3: fix padding for long cSHAKE parameters</li>
<li><a href="https://togithub.com/golang/crypto/commit/c17aa50fbd32393e5d52fa65ca51cbfff0a75aea"><code>c17aa50</code></a> sha3: avoid buffer copy</li>
<li>Additional commits viewable in <a href="https://togithub.com/golang/crypto/compare/v0.21.0...v0.31.0">compare view</a></li>
</ul>
</details>
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</details>

- fix some deprecation warnings
- have bodys return as the type they, a bytes.Buffer
- add new handle to return a bytes.Buffer instead of Reader

This connects the logger passed in by users with options to the
auth library.