Fix broken website link.

website/docs/pants.mdx

diff --git a/website/docs/pants.mdx b/website/docs/pants.mdx
index aa917a1..fcf2860 100644
--- a/website/docs/pants.mdx
+++ b/website/docs/pants.mdx
@@ -265,7 +265,7 @@
 into a baseline, or keep mypy enabled for just those packages during the
 transition.
 
-[Migrating from Mypy](./migrating-from-mypy.mdx) covers the checker-level
+[Migrating from Mypy](./migrate/mypy/index.mdx) covers the checker-level
 differences — command-line equivalents, suppression syntax, and behavioral
 divergences — independently of Pants.