Automated update to Github CI to rustc nightly-2025-12-13

Update Nightly Rustc Bot · Update Nightly Rustc Bot · commit a2f2b6ebfb4c · 2025-12-15T00:42:00.000Z
diff --git a/nightly-version b/nightly-version
@@ -1 +1 @@
-nightly-2025-09-27
+nightly-2025-12-13
