Prepare azidentity v1.4.0-beta.3 for release (Azure#21331)

Author: chlowell

sdk/azidentity/CHANGELOG.md

@@ -1,17 +1,11 @@
 # Release History
 
-## 1.4.0-beta.3 (Unreleased)
-
-### Features Added
-
-### Breaking Changes
+## 1.4.0-beta.3 (2023-08-08)
 
 ### Bugs Fixed
 * One invocation of `AzureCLICredential.GetToken()` and `OnBehalfOfCredential.GetToken()`
   can no longer make two authentication attempts
 
-### Other Changes
-
 ## 1.4.0-beta.2 (2023-07-14)
 
 ### Other Changes