[IMP] website_slides,_profile: Improve elearning UX

This commit changes:
  - In elearning homepage, change "Heroes of the week"
    to "leaderboard of the week"
  - In user profile, change "Rank: Master" to
    "Current Rank: Master"
  - In the "Edit Profile" view, remove the required
    on the description text area

Task: #1961116
PR: #32621

Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>