Fix typo.

Author: fnando

lib/browser/methods/platform.rb

@@ -30,7 +30,7 @@ def ios7?
  ios? && !!(ua =~ /OS 7/)
  end
 
- # Detect if is iOS7.
+ # Detect if is iOS8.
  def ios8?
  ios? && !!(ua =~ /OS 8/)
  end