Remove `pattern` from `location.image` field

What does this MR do?

This MR removes pattern on location.image and location.default_branch_image.

Related to container scanning parsing errors when no tag i... (gitlab-org/gitlab#372273 - closed)

What are the relevant issue numbers?

Checklist

• Ensure changes can be built upon without requiring a breaking change, see Building for Extensibility.
• Review and add/update tests for this feature/bug.
• Add an entry to the CHANGELOG if required, with the appropriate version. See Classifying Changes.
• Assign the MR to the appropriate person/people for review.

Closes container scanning parsing errors when no tag i... (gitlab-org/gitlab#372273 - closed)