Fix grammar

wiki/src/contribute/mission.html

@@ -37,7 +37,7 @@ whenever you need extra privacy in this digital world.</p>
 
 <p>We build liberating technology to put people in control of their
 digital lives. We make it simple for our users to make informed
-decisions depending on their situations. <strong>The most vulnerable and
+decisions depending on their situation. <strong>The most vulnerable and
 oppressed people are the most in need of privacy and security.</strong></p>
 
 <h3>Ecosystemic</h3>