Update changelogs from fern repo (#4443)

Co-authored-by: iamnamananand996 <31537362+iamnamananand996@users.noreply.github.com>

Author: fern-support

fern/products/sdks/overview/rust/changelog/2026-03-20.mdx

@@ -1,3 +1,10 @@
+## 0.20.3
+**`(fix):`** Fix dynamic snippets and wire tests generating `Some(Some(value))` for optional+nullable
+fields. Since `Type.option()` now collapses `Option<Option<T>>` to `Option<T>`, the
+literal mapper must also collapse nested optional/nullable wrapping to produce `Some(value)`
+instead of `Some(Some(value))`.
+
+
 ## 0.20.2
 **`(fix):`** Fix inlined request type documentation to use the schema-level description from the
 OpenAPI spec instead of a generic fallback. Previously, all inlined request types used