chore(newsletter): remove links

I'm shelving the newsletter until a better time, and removing it from
the website's navigation. The page itself remains, though, in case I
want to revisit this.

_includes/navigation.html

@@ -21,11 +21,6 @@
           <i class="twa twa-pencil"></i> <span class="nav-item-label">Blog</span>
         </a>
       </li>
-      <li>
-        <a class="nav-item{% if active == 'newsletter' %} active{% endif %}" href="/the-long-term">
-          <i class="twa twa-love-letter"></i> <span class="nav-item-label">The Long Term</span>
-        </a>
-      </li>
       <li>
         <a class="nav-item{% if active == 'about' %} active{% endif %}" href="/about">
           <i class="twa twa-man-raising-hand-light-skin-tone"></i> <span class="nav-item-label">About</span>

colophon.html

@@ -25,7 +25,6 @@ <h1>Colophon</h1>
   <h3>Privacy statement</h3>
   <p>This is a static website; it does not use cookies.</p>
   <p>I use <a href="https://plausible.io">Plausible</a>, a privacy-focused analytics tool, to collect limited non-personally identifiable stats on visitors. Please see <a href="https://plausible.io/data-policy">their data policy</a>.</p>
-  <p>I also use <a href="https://buttondown.email">Buttondown</a> as my newsletter service, and if you decide to subscribe to The Long Term, your email address will be stored with them. Please see <a href="https://buttondown.email/legal/privacy">their privacy policy</a>.</p>
 </section>
 
 <section>

index.html

@@ -18,5 +18,5 @@
   </figure>
 </div>
 <section>
-  <p>The photos above are from a yet-untitled ongoing project documenting family life. If you're curious about this project's development, please consider subscribing to <a href="/the-long-term">The Long Term</a>, which will document it.</p>
+  <p>The photos above are from a yet-untitled ongoing project documenting family life.</p>
 </section>