Use the right identifier for the version number substitution

browser/app/macbuild/Contents/Info.plist.in

@@ -82,7 +82,7 @@
 	<key>CFBundlePackageType</key>
 	<string>APPL</string>
 	<key>CFBundleShortVersionString</key>
-	<string>@BROWSER_VERSION@</string>
+	<string>@APP_VERSION@</string>
 	<key>CFBundleSignature</key>
 	<string>MOZB</string>
 	<key>CFBundleURLTypes</key>