fix(xo-web): relax pattern for bucket

[fbeauchamp]

bucket from AWS follow some naming convention, but other providers are more relaxed.
removing the regex check will allow the user to tests connecting and see the backend specific error message

Check list

Check if done, if not relevant leave unchecked.

• PR reference the relevant issue (e.g. Fixes #007 or See xoa-support#42)
• if UI changes, a screenshot has been added to the PR
• documentation updated
• CHANGELOG.unreleased.md:
  • enhancement/bug fix entry added
  • list of packages to release updated (${name} v${new version})
• I have tested added/updated features (and impacted code)
  • unit tests (e.g. cron/parse.spec.js)
  • if xo-server API changes, the corresponding test has been added to/updated on xo-server-test
  • at least manual testing

Process

1. create a PR as soon as possible
2. mark it as WiP: (Work in Progress) if not ready to be merged
3. when you want a review, add a reviewer (and only one)
4. if necessary, update your PR, and re- add a reviewer

From the Four Agreements:

1. Be impeccable with your word.
2. Don't take anything personally.
3. Don't make assumptions.
4. Always do your best.