build(deps): Bump proc-macro2 from 1.0.76 to 1.0.78 (#408)

Bumps [proc-macro2](https://github.com/dtolnay/proc-macro2) from 1.0.76
to 1.0.78.
<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>1.0.78</h2>
<ul>
<li>Expose <a
href="https://doc.rust-lang.org/1.71.0/proc_macro/struct.Span.html#method.byte_range">Span::byte_range</a>
(<a
href="https://redirect.github.com/dtolnay/proc-macro2/issues/442">#442</a>)</li>
</ul>
<h2>1.0.77</h2>
<ul>
<li>Add a function to reset thread-local span data (<a
href="https://redirect.github.com/dtolnay/proc-macro2/issues/438">#438</a>,
thanks <a
href="https://github.com/buchgr"><code>@​buchgr</code></a>)</li>
</ul>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/dtolnay/proc-macro2/commit/d850a1db5e3fe7732d62cacbfc4145e496c2a80e"><code>d850a1d</code></a>
Release 1.0.78</li>
<li><a
href="https://github.com/dtolnay/proc-macro2/commit/6cefaec285bf51ad9476a52e1676ef698fe2ba9c"><code>6cefaec</code></a>
Merge pull request <a
href="https://redirect.github.com/dtolnay/proc-macro2/issues/442">#442</a>
from dtolnay/byterange</li>
<li><a
href="https://github.com/dtolnay/proc-macro2/commit/10827679cdb6c7cbcade2d90cbebbb77484a0570"><code>1082767</code></a>
Expose Span::byte_range</li>
<li><a
href="https://github.com/dtolnay/proc-macro2/commit/da1be4d1aea56dcfd5e515b7bded9283323320f5"><code>da1be4d</code></a>
Release 1.0.77</li>
<li><a
href="https://github.com/dtolnay/proc-macro2/commit/69fee37f91d24bc662ff46dad87dbc4c35991698"><code>69fee37</code></a>
Merge pull request <a
href="https://redirect.github.com/dtolnay/proc-macro2/issues/440">#440</a>
from dtolnay/example</li>
<li><a
href="https://github.com/dtolnay/proc-macro2/commit/66a3ef00b8cd3ba934f3e43720413aa927c018e7"><code>66a3ef0</code></a>
Raise minimum tested compiler to 1.63</li>
<li><a
href="https://github.com/dtolnay/proc-macro2/commit/d2441c39a8af23f605cb4fe917e2c2884262503f"><code>d2441c3</code></a>
Add example code for invalidate_current_thread_spans</li>
<li><a
href="https://github.com/dtolnay/proc-macro2/commit/43011bf8edf29c4668fbc3619243485f2e1d0f52"><code>43011bf</code></a>
Ensure invalidate_current_thread_spans has docs even if proc-macro
disabled</li>
<li><a
href="https://github.com/dtolnay/proc-macro2/commit/7e7bb0fbc94b94a14292e56d0b9cfbe2558a479c"><code>7e7bb0f</code></a>
Improve documentation of invalidate_current_thread_spans</li>
<li><a
href="https://github.com/dtolnay/proc-macro2/commit/64778fc68ff4dfa0e17e2de566206c7d441116b8"><code>64778fc</code></a>
Move invalidate_current_thread_spans to proc_macro2::extra</li>
<li>Additional commits viewable in <a
href="https://github.com/dtolnay/proc-macro2/compare/1.0.76...1.0.78">compare
view</a></li>
</ul>
</details>
<br />


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