Update changelogs from fern repo (#5139)

Co-authored-by: dsinghvi <10870189+dsinghvi@users.noreply.github.com>

Author: fern-support

fern/products/sdks/generators/python/changelog/2026-04-24.mdx

@@ -0,0 +1,8 @@
+## 5.6.0
+**`(feat):`** Support `x-fern-default` as fallback value for parameters in generated Python SDKs.
+When a header, query parameter, or path parameter has a `clientDefault` value in the IR,
+the generated Python function signature makes that parameter optional with the default
+value automatically applied. This enables patterns like optional API version headers
+that fall back to a pinned version.
+
+