Be more explicit

And fix very old typo 'is' → 'if'!

wiki/src/contribute/how/documentation/release_notes/template.mdwn

@@ -82,7 +82,7 @@ Follow our installation instructions:
   - [[Install from macOS|install/mac]]
   - [[Install from Linux|install/linux]]
 
-<div class="caution"><p>All the data on this USB stick will be lost is
+<div class="caution"><p>The Persistent Storage on the USB stick will be lost if
 you install instead of upgrading.</p></div>
 
 ## To download only