fix(users): remove blank params from user form

[wJoenn]

Summary of changes and context

The favourite language input in the user form is as follow

<%= f.select :favourite_language, Snippet::LANGUAGES.invert.to_a, { prompt: "", selected: @user.favourite_language }, class: "input" %>

If a user has no language then @user.favourite_language is nil and when a form input is nil Rails converts it to an empty string.
This means that as long as a user hasn't selected a favourite language, any update he tries to make on his user model will fail because the front sends { favourite_language: "" } which does not pass the validation

  validates :favourite_language, inclusion: { in: Snippet::LANGUAGES.keys.map(&:to_s) }, allow_nil: true

This PR fixes this by appending #compact_blank to the params.require().permit in the UsersController which removes blank params

Sanity checks

• Linters pass
• Tests pass
• Related GitHub issues are linked in the description

[pil0u]

C'est mieux 🚀 (enfin je pense)