Updated changelog for 1.38.0 release (#3133)

Author: JonasKunz

CHANGELOG.asciidoc

@@ -20,8 +20,11 @@ endif::[]
 
 === Unreleased
 
+[[release-notes-1.x]]
+=== Java Agent version 1.x
+
 [[release-notes-1.38.0]]
-==== 1.38.0 - YYYY/MM/DD
+==== 1.38.0 - 2023/05/04
 
 [float]
 ===== Features
@@ -33,9 +36,6 @@ endif::[]
 ===== Bug fixes
 * Do not use proxy to retrieve cloud metadata - {pull}3108[#3108]
 
-[[release-notes-1.x]]
-=== Java Agent version 1.x
-
 [[release-notes-1.37.0]]
 ==== 1.37.0 - 2023/04/11