CHANGELOG: fix zstd experimental (#5047)

**Which issue(s) this PR fixes**: 
None.

**What this PR does / why we need it**: 
Fix v1.19.0 CHANGELOG.
What is experimental is out_forward.
See #4896.

**Docs Changes**:
Not needed.

**Release Note**: 
Not needed.

Signed-off-by: Daijiro Fukuda <[email protected]>

Author: daipom

CHANGELOG.md

@@ -9,8 +9,8 @@ New features:
 * Add zstd compression support https://github.com/fluent/fluentd/pull/4657
   * Buffer: add `zstd` to `compress` option.
   * out_file: add `zstd` to `compress` option.
-  * out_forward: add `zstd` to `compress` option.
-  * in_forward: support `zstd` format. (Experimental)
+  * out_forward: add `zstd` to `compress` option. (Experimental)
+  * in_forward: support `zstd` format.
 * buffer: add feature to evacuate chunk files when retry limit
   https://github.com/fluent/fluentd/pull/4986
 * out_http: TLS1.3 support