Describe the bug
Related to #8923, #8488

Since the VAPID keys generators were moved to the core gem, the rake tasks no longer work if the decidim-dev gem is not installed.

This happens because this task file requires the "webpush" gem:

But this dependency is only listed in the decidim-dev gem:

To Reproduce
Steps to reproduce the behavior:

1. bundle install --without development test
2. bundle exec rails db:migrate
3. See error

Expected behavior
I would expect to be able to run the Decidim or Rails rake tasks when the decidim-dev gem is not installed.

Screenshots
N/A

Stacktrace
See the error.

Extra data (please complete the following information):

• Device: (any)
• Device OS: (any)
• Browser: (any)
• Decidim Version: 0.27.0.dev
• Decidim installation: staging environments

Additional context
Ping @quinHD