update changelog

CHANGELOG-EE

 v7.13.3
   - Merge community edition changes for version 7.13.3
   - Improved validation for an approver
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-v7.13.2
-  - Merge community edition changes for version 7.13.2
-v 7.13.3
-  - Merge community edition changes for version 7.13.3
   - Don't resend admin email to everyone if one delivery fails
   - Added migration for removing of invalid approvers
 v 7.13.2
-v7.13.3
-  - Merge community edition changes for version 7.13.3
-  - Improved validation for an approver
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-v7.13.2
   - Merge community edition changes for version 7.13.2
   - Fix group web hook