chore: refer to the prefix

Author: KazuCocoa

lib/appium_lib_core/driver.rb

@@ -707,7 +707,7 @@ def set_automation_name_if_nil
       end
 
       def get_cap(name)
-        name_with_prefix = "appium:#{name}"
+        name_with_prefix = "#{::Appium::Core::Base::Bridge::APPIUM_PREFIX}#{name}"
         @caps[convert_to_symbol name] ||
           @caps[name] ||
           @caps[convert_to_symbol name_with_prefix] ||