Update CHANGELOG to prepare for 1.0.0b6 release (Azure#24792)

Author: lzchen

sdk/monitor/azure-monitor-opentelemetry-exporter/CHANGELOG.md

@@ -1,6 +1,6 @@
 # Release History
 
-## 1.0.0b6 (Unreleased)
+## 1.0.0b6 (2022-06-10)
 
 ### Features Added
 - Implement log exporter using experimental OT logging sdk
@@ -16,10 +16,6 @@
 - Update to OpenTelemetry api/sdk 1.12.0rc1
     ([#24619](https://github.com/Azure/azure-sdk-for-python/pull/24619))
 
-### Bugs Fixed
-
-### Other Changes
-
 ## 1.0.0b5 (2021-10-05)
 
 ### Features Added