Un-swallow error message in Sentry issue sync worker

What does this MR do?

This MR surfaces the error message in the logs when a GitLab issue fails to link with a Sentry issue. This may be a common occurrence (like when a Sentry integration with GitLab is not configured), but when the failure is unexpected, there is currently not enough info to debug. This un-swallows some of that info.

Related to debugging for #37307 (closed).

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