Update to Lean 4.20.1 (#172)

TwoFX · web-flow · commit 1bfcba157d58 · 2025-06-05T08:57:59.000+02:00
diff --git a/lean-toolchain b/lean-toolchain
@@ -1 +1 @@
-leanprover/lean4:v4.19.0
+leanprover/lean4:v4.20.1
