Prepare Azure.Core 1.21 release (Azure#25110)

Author: pakrym

sdk/core/Azure.Core.Experimental/CHANGELOG.md

@@ -1,14 +1,6 @@
 # Release History
 
-## 0.1.0-preview.18 (Unreleased)
-
-### Features Added
-
-### Breaking Changes
-
-### Bugs Fixed
-
-### Other Changes
+## 0.1.0-preview.18 (2021-11-03)
 
 ## 0.1.0-preview.17 (2021-10-01)
 

sdk/core/Azure.Core/CHANGELOG.md

@@ -1,14 +1,6 @@
 # Release History
 
-## 1.21.0-beta.1 (Unreleased)
-
-### Features Added
-
-### Breaking Changes
-
-### Bugs Fixed
-
-### Other Changes
+## 1.21.0 (2021-11-03)
 
 ## 1.20.0 (2021-10-01)
 

sdk/core/Azure.Core/src/Azure.Core.csproj

@@ -2,7 +2,7 @@
   <PropertyGroup>
     <Description>This is the implementation of the Azure Client Pipeline</Description>
     <AssemblyTitle>Microsoft Azure Client Pipeline</AssemblyTitle>
-    <Version>1.21.0-beta.1</Version>
+    <Version>1.21.0</Version>
     <!--The ApiCompatVersion is managed automatically and should not generally be modified manually.-->
     <ApiCompatVersion>1.20.0</ApiCompatVersion>
     <PackageTags>Microsoft Azure Client Pipeline</PackageTags>