Use default license path in seeds

What does this MR do?

Before

without GITLAB_LICENSE_FILE in production env task looked for file at default location as stated in docs, for development env it had written "Skipped" message and quit the task.

After

without GITLAB_LICENSE_FILE in production env NO CHANGES. for development env - behaves as in production, buts adds "Skipped" message if no valid license candidate files was found.

Why

currently rake db:seed_fu doesn't work without GITLAB_LICENSE_FILE explicitly specified in dev env. Which makes reloading seeds less convenient and inconsistent with the docs.

Screenshots (strongly suggested)

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