Update changelog

Author: nfagerlund

CHANGELOG.md

@@ -2,6 +2,11 @@
 
 ## Enhancements
 * Adds `RunPreApplyCompleted` run status by @uk1288 [#727](https://github.com/hashicorp/go-tfe/pull/727)
+* Added BETA support for saved plan runs, by @nfagerlund [#724](https://github.com/hashicorp/go-tfe/pull/724)
+    * New `SavePlan` fields in `Run` and `RunCreateOptions`
+    * New `RunPlannedAndSaved` `RunStatus` value
+    * New `PlannedAndSavedAt` field in `RunStatusTimestamps`
+    * New `RunOperationSavePlan` constant for run list filters
 
 # v1.28.0