docs: update to next version [BUMP BETA] (#4493)

platform/docs/versioned_docs/version-3.9/migration-guide/3p8-to-3p9/6-RTSTRUCT.md

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+---
+id: 6-rtstruct
+title: RTSTRUCT
+sidebar_position: 6
+---
+
+
+
+# RTStructure Set has transitioned from VTK actors to SVG.
+
+We have transitioned from VTK-based rendering to SVG-based rendering for RTStructure Set contours. This change should not require any modifications to your codebase. We anticipate improved stability and speed in our contour rendering.
+
+As a result of this update, viewports rendering RTStructure Sets will no longer convert to volume viewports. Instead, they will remain as stack viewports.
+
+
+Read more in Pull Requests:
+- https://github.com/OHIF/Viewers/pull/4074
+- https://github.com/OHIF/Viewers/pull/4157