Use 'General Change.md' as default MR description
Summary
Follow-up to !585 (merged)
Renames 'General Change.md' to 'Default.md' so it is automatically used as the default merge request description.
Related documentation: https://docs.gitlab.com/ee/user/project/description_templates.html#supported-variables-in-merge-request-templates
This ensures that the '%{first_multiline_commit}' variable works as expected, given the note in the documentation:
This feature is available only for the default template.
The default template docs state that the file needs to be named 'Default.md' (case insensitive).
Edited by Mitchell Nielsen