[FIX] website: use currentTarget onLangChangeClick

Before this commit, in case of Google Translate is enable, some content
can be wrapped in extra node.

Use currentTarget is more secure to get the right element clicked.

**Steps to reproduce:**
1. Add a website and multiple language
2. Create a page in 2 languages
3. Visit the website in Chrome and enable the translation by Google translate
4. Change the language and you should get an error similar to:

Error:
Uncaught TypeError: Cannot read property 'replace' of undefined

closes odoo/odoo#62849

X-original-commit: a2ebc05c
Signed-off-by: Jérémy Kersten (jke) <jke@openerp.com>