Automated update to Github CI to rustc nightly-2025-09-21

Update Nightly Rustc Bot · Update Nightly Rustc Bot · commit d018dd642f59 · 2025-09-22T02:07:20.000Z
diff --git a/nightly-version b/nightly-version
@@ -1 +1 @@
-nightly-2024-08-04
+nightly-2025-09-21
