Update oauth2 to 1.4.4 fixing faraday constraint

What does this MR do?

Fixes an unsatisfiable constraint in current Gemfile.lock, where oauth2 wants < 0.16.0 but we are already at 0.17.3

See https://github.com/oauth-xx/oauth2/compare/v1.4.1...v1.4.4 for a list of changes

Identified by attempting to run

bundle update validates_hostname

and getting the output

Bundler could not find compatible versions for gem "faraday":
  In snapshot (Gemfile.lock):
    faraday (= 0.17.3)
  In Gemfile:
    faraday (~> 0.12)
    acme-client (~> 2.0.5) was resolved to 2.0.5, which depends on
      faraday (~> 0.9, >= 0.9.1)
    faraday_middleware-aws-signers-v4 was resolved to 0.1.7, which depends on
      faraday (~> 0.9)
    oauth2 (~> 1.4) was resolved to 1.4.1, which depends on
      faraday (>= 0.8, < 0.16.0)
Running `bundle update` will rebuild your snapshot from scratch, using only
the gems in your Gemfile, which may resolve the conflict.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• [-] Merge request performance guidelines
• [-] Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

• [-] Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team