build(deps): bump html2rss-configs to 71981af in the rubygems group (#931) [skip ci]

Bumps the rubygems group with 1 update:
[html2rss-configs](https://github.com/html2rss/html2rss-configs).

Updates `html2rss-configs` from `24d38d6` to `71981af`
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/html2rss/html2rss-configs/commit/71981aff28d88e4553c206d78bf54d5633bcdd19"><code>71981af</code></a>
chore(deps): bump html2rss from <code>e0dca5b</code> to
<code>v0.18.0</code> (<a
href="https://redirect.github.com/html2rss/html2rss-configs/issues/302">#302</a>)</li>
<li>See full diff in <a
href="https://github.com/html2rss/html2rss-configs/compare/24d38d64e578e93340e228c7bbfd2b187a2b94b6...71981aff28d88e4553c206d78bf54d5633bcdd19">compare
view</a></li>
</ul>
</details>
<br />


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Gemfile.lock

@@ -1,6 +1,6 @@
 GIT
   remote: https://github.com/html2rss/html2rss-configs
-  revision: 24d38d64e578e93340e228c7bbfd2b187a2b94b6
+  revision: 71981aff28d88e4553c206d78bf54d5633bcdd19
   specs:
     html2rss-configs (0.2.0)
       html2rss