doc: save chore/remove-data-files-btn PR desc

chore-remove-data-files-btn-pr-desc.md

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+## Overview
+
+Remove the unnecessary `.data-files-btn` class.
+
+<details><summary>Details</summary>
+
+This class is assigned to buttons that:
+- **either** have Bootstrap btn-primary (in which case the `.workbench-content .btn-primary` styles it)
+- **or** are our custom `<Button>` (in which case the `composes: c-button` styles it)
+
+</details> 
+
+## Related
+
+* [WP-XYZ](https://tacc-main.atlassian.net/browse/WP-XYZ)
+
+## Changes
+
+* remove assignment of class
+* remove styles for class
+
+## Testing
+
+Verify these buttons' style is unchanged:
+- "Data Files" → [Add +] button
+- "Data Files" → select a file → [Copy]
+
+## UI
+
+https://github.com/user-attachments/assets/e6df8ed7-9228-4e2b-8eaa-a9f8e94e21f5
+
+https://github.com/user-attachments/assets/ef4a2dad-0dd7-4b82-a4bc-e8619b73484a