Update changelogs from fern repo (#389)

Author: fern-support

fern/products/sdks/overview/go/changelog/2025-08-07.mdx

@@ -1,3 +1,7 @@
+## 1.5.7-rc0
+**`(fix):`** Fix go sse event stream handling.
+
+
 ## 1.5.6
 **`(chore):`** Publishing new version after reverting bad commit that released an rc version 1.5.5-rc0.