Bump proc-macro2 from 1.0.54 to 1.0.56 (#2775)

Bumps [proc-macro2](https://github.com/dtolnay/proc-macro2) from 1.0.54 to 1.0.56.
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a href="https://github.com/dtolnay/proc-macro2/releases">proc-macro2's releases</a>.</em></p>
<blockquote>
<h2>1.0.56</h2>
<ul>
<li>Circumvent clippy::octal_escapes lint inside generated string and byte-string literals (<a href="https://redirect.github.com/dtolnay/proc-macro2/issues/363">#363</a>, <a href="https://redirect.github.com/dtolnay/proc-macro2/issues/380">#380</a>)</li>
<li>Provide RefUnwindSafe impls for compilers older than 1.58 (<a href="https://redirect.github.com/dtolnay/proc-macro2/issues/382">#382</a>)</li>
</ul>
<h2>1.0.55</h2>
<ul>
<li>Set a meaningful <code>Span</code> for literals produced via the <code>FromStr</code> impl of <code>Literal</code> (<a href="https://redirect.github.com/dtolnay/proc-macro2/issues/378">#378</a>)</li>
<li>Implement <code>Literal::subspan</code> in non-macro contexts when &quot;span-locations&quot; feature is enabled (<a href="https://redirect.github.com/dtolnay/proc-macro2/issues/379">#379</a>)</li>
</ul>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a href="72ee0b3b05"><code>72ee0b3</code></a> Release 1.0.56</li>
<li><a href="ddf769275b"><code>ddf7692</code></a> Merge pull request <a href="https://redirect.github.com/dtolnay/proc-macro2/issues/382">#382</a> from dtolnay/refunwindsafe</li>
<li><a href="cda93c5eef"><code>cda93c5</code></a> Ensure data structures are RefUnwindSafe on all versions of Rust</li>
<li><a href="e82b0749f8"><code>e82b074</code></a> Merge pull request <a href="https://redirect.github.com/dtolnay/proc-macro2/issues/381">#381</a> from dtolnay/escape0</li>
<li><a href="7efc1c4db2"><code>7efc1c4</code></a> Implement consistent behavior for Literal::string on all versions of Rust</li>
<li><a href="9c092a3284"><code>9c092a3</code></a> Merge pull request <a href="https://redirect.github.com/dtolnay/proc-macro2/issues/380">#380</a> from dtolnay/octalescape</li>
<li><a href="6c216275bc"><code>6c21627</code></a> Fix literal_string test on rustc older than 1.61</li>
<li><a href="5d3e58b9c6"><code>5d3e58b</code></a> Ignore octal_escapes clippy lint in test</li>
<li><a href="57b4db1f78"><code>57b4db1</code></a> Circumvent clippy::octal_escapes lint in generated literals</li>
<li><a href="d827973a8d"><code>d827973</code></a> Add regression test of \0 escaping for issue 363</li>
<li>Additional commits viewable in <a href="https://github.com/dtolnay/proc-macro2/compare/1.0.54...1.0.56">compare view</a></li>
</ul>
</details>
<br />


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Cargo.lock

@@ -3145,9 +3145,9 @@ checksum = "dc375e1527247fe1a97d8b7156678dfe7c1af2fc075c9a4db3690ecd2a148068"
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.54"
+version = "1.0.56"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e472a104799c74b514a57226160104aa483546de37e839ec50e3c2e41dd87534"
+checksum = "2b63bdb0cd06f1f4dedf69b254734f9b45af66e4a031e42a7480257d9898b435"
 dependencies = [
  "unicode-ident",
 ]