Update changelogs from fern repo (#2533)

Co-authored-by: tstanmay13 <29681256+tstanmay13@users.noreply.github.com>

Author: fern-support

fern/products/sdks/overview/java/changelog/2025-12-04.mdx

@@ -1,3 +1,7 @@
+## 3.21.1
+**`(fix):`** Fix header parameters with `x-fern-parameter-name` to use the correct HTTP header name (wire value) instead of the SDK parameter name.
+
+
 ## 3.21.0
 **`(fix):`** Remove unused kotlin-stdlib from Gradle base image to address CVE-2020-29582 in container.