Fix /about/ page images (#1564)

pages/about.html

@@ -25,7 +25,7 @@ hidedesc: true
 <div class="row">
 
 {% include team.html
-avatar="burung.jpg"
+avatar="burung.png"
 name="Burung Hantu"
 role="Founder"
 bio="I founded PrivacyTools in 2015 to share resources and tools, allowing users to avoid international mass-surveillance programs."
@@ -59,7 +59,7 @@ mastodon="https://social.privacytools.io/@blacklight447"
 %}
 
 {% include team.html
-avatar="danarel.jpg"
+avatar="danarel.png"
 name="Dan Arel"
 role="Blogging & Education"
 bio="I'm an author, columnist, and privacy advocate whose work has appeared in Time, Huff Post, OpenSource, and more."
@@ -102,7 +102,7 @@ keys="https://gitea.blesmrt.net/mikaela/shell-things/src/branch/master/.mikaela/
 %}
 
 {% include team.html
-avatar="nitrohorse.jpg"
+avatar="nitrohorse.png"
 name="Andreas Basurto"
 nick="nitrohorse"
 role="Developer"
@@ -114,7 +114,7 @@ blog="nitrohorse"
 %}
 
 {% include team.html
-avatar="trai_dep.jpg"
+avatar="trai_dep.png"
 name="trai_dep"
 role="Subreddit Mod"
 bio="I'm the moderator at r/Privacy and r/privacytoolsIO. Day to day, I am also – <i>irony alert</i> – an (ethical) digital marketer."