Bump bleach from 3.1.1 to 3.1.4

Bumps [bleach](https://github.com/mozilla/bleach) from 3.1.1 to 3.1.4.
<details>
<summary>Changelog</summary>
<p><em>Sourced from <a href="https://github.com/mozilla/bleach/blob/master/CHANGES">bleach's changelog</a>.</em></p>
<blockquote>
<h2>Version 3.1.4 (March 24th, 2020)</h2>
<p><strong>Security fixes</strong></p>
<ul>
<li>
<p><code>bleach.clean</code> behavior parsing style attributes could result in a
regular expression denial of service (ReDoS).</p>
<p>Calls to <code>bleach.clean</code> with an allowed tag with an allowed
<code>style</code> attribute were vulnerable to ReDoS. For example,
<code>bleach.clean(..., attributes={'a': ['style']})</code>.</p>
<p>This issue was confirmed in Bleach versions v3.1.3, v3.1.2, v3.1.1,
v3.1.0, v3.0.0, v2.1.4, and v2.1.3. Earlier versions used a similar
regular expression and should be considered vulnerable too.</p>
<p>Anyone using Bleach &lt;=v3.1.3 is encouraged to upgrade.</p>
<p><a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1623633">https://bugzilla.mozilla.org/show_bug.cgi?id=1623633</a></p>
</li>
</ul>
<p><strong>Backwards incompatible changes</strong></p>
<ul>
<li>Style attributes with dashes, or single or double quoted values are
cleaned instead of passed through.</li>
</ul>
<p><strong>Features</strong></p>
<p>None</p>
<p><strong>Bug fixes</strong></p>
<p>None</p>
<h2>Version 3.1.3 (March 17th, 2020)</h2>
<p><strong>Security fixes</strong></p>
<p>None</p>
<p><strong>Backwards incompatible changes</strong></p>
<p>None</p>
<p><strong>Features</strong></p>
<ul>
<li>
<p>Add relative link to code of conduct. (<a href="https://github-redirect.dependabot.com/mozilla/bleach/issues/442">#442</a>)</p>
</li>
<li>
<p>Drop deprecated 'setup.py test' support. (<a href="https://github-redirect.dependabot.com/mozilla/bleach/issues/507">#507</a>)</p>
</li>
</ul>
</tr></table> ... (truncated)
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a href="https://github.com/mozilla/bleach/commit/6e74a5027b57055cdaeb040343d32934121392a7"><code>6e74a50</code></a> Update for v3.1.4 release</li>
<li><a href="https://github.com/mozilla/bleach/commit/d6018f2539d271963c3e7f54f36ef11900363c69"><code>d6018f2</code></a> fix bug 1623633</li>
<li><a href="https://github.com/mozilla/bleach/commit/fc77027e67cc04aff6f4d4885358705f98ad20f4"><code>fc77027</code></a> Merge branch 'v3.1.0-branch'</li>
<li><a href="https://github.com/mozilla/bleach/commit/e4b1c50e098c33f82c862a34bb2a40f9c4458f46"><code>e4b1c50</code></a> Update for v3.1.3 release</li>
<li><a href="https://github.com/mozilla/bleach/commit/59cc502cee44bd18adc78619e6baed7a108c3ba1"><code>59cc502</code></a> Update for v3.1.2 release</li>
<li><a href="https://github.com/mozilla/bleach/commit/3f39d489ab7a1b38df8c245e9bd66217c1698369"><code>3f39d48</code></a> add wheel to requirements-dev</li>
<li><a href="https://github.com/mozilla/bleach/commit/175f67740e7951e1d80cefb7831e6c3e4efeb986"><code>175f677</code></a> fix bug 1621692</li>
<li><a href="https://github.com/mozilla/bleach/commit/78a06726dd6c72a42c90c1f7a8fa5d21ebcfa587"><code>78a0672</code></a> Update for v3.1.2 release</li>
<li><a href="https://github.com/mozilla/bleach/commit/7b625ff9f6888a08037700269fb23e3ef863b8a7"><code>7b625ff</code></a> add wheel to requirements-dev</li>
<li><a href="https://github.com/mozilla/bleach/commit/e4e9e21e7aebff40c88fafa4319bba4636a602d9"><code>e4e9e21</code></a> fix bug 1621692</li>
<li>Additional commits viewable in <a href="https://github.com/mozilla/bleach/compare/v3.1.1...v3.1.4">compare view</a></li>
</ul>
</details>
<br />


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</details>

Looks like bleach is up-to-date now, so this is no longer needed.