Fix HTML

wiki/src/donate.html

@@ -12,7 +12,7 @@
 
   <h1>Protect freedom in the digital age</h1>
 
-  <h2>Fight surveillance and censorship!</h1>
+  <h2>Fight surveillance and censorship!</h2>
 
   <p>At Tails, we build liberating technology to put people in control
   of their digital lives:</p>