changed thumbnail theme

Signed-off-by: B_Kishore <85435355+kishore08-07@users.noreply.github.com>

Author: kishore08-07

src/collections/programs/hacktoberfest-2025/index.mdx

@@ -1,8 +1,8 @@
 ---
 title: "Hacktoberfest 2025"
 description: "Designing with Meshery - Prepare for Hacktoberfest with Layer5 MeshMates and Maintainers. Join seasoned open source maintainers, hack through easy issues, and grow your skills. Discover Newcomers resources and explore the Layer5 Community Handbook."
-thumbnail: ./HF-Stacked-Color-Light.svg
-darkthumbnail: ./HF-Stacked-Color-Dark.svg
+thumbnail: ./HF-Stacked-Color-Dark.svg
+darkthumbnail: ./HF-Stacked-Color-Light.svg
 permalink: "hacktoberfest/2025"
 program: "Hacktoberfest"
 programSlug: "hacktoberfest"