Resolve "Error 502 when viewing billing page after trial ends"

What does this MR do?

Fixes the 502 error whenever a user goes to a group or a personal billing page after a trial ends.

Regression is introduced by this MR on 2019, August 16 by the removal of the learn_more_text variable

Resolves the following issues:

• https://gitlab.com/gitlab-com/support-forum/issues/4809
• Main issue #31364 (closed)
• Also see a full list of zendesk issues in the #31364 (closed)

Screenshots

Error as reported by users	Error in the development environment
lC4jpMUMpt

Regression Error fixed

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• 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

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