Release Google.Cloud.Bigtable.Admin.V2 version 3.20.0 (#13530)

Changes in this release:

### New features

- Add support for Cloud Bigtable Row Affinity in App Profiles ([commit 5a08cf4](https://github.com/googleapis/google-cloud-dotnet/commit/5a08cf49142149d6d38f5a0eea517f362df7eb11))

apis/Google.Cloud.Bigtable.Admin.V2/Google.Cloud.Bigtable.Admin.V2/Google.Cloud.Bigtable.Admin.V2.csproj

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <Version>3.19.0</Version>
+    <Version>3.20.0</Version>
     <TargetFrameworks>netstandard2.0;net462</TargetFrameworks>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <Description>Recommended Google client library to access the Google Cloud Bigtable Instance and Table Admin APIs.</Description>

apis/Google.Cloud.Bigtable.Admin.V2/docs/history.md

@@ -1,5 +1,11 @@
 # Version history
 
+## Version 3.20.0, released 2024-09-16
+
+### New features
+
+- Add support for Cloud Bigtable Row Affinity in App Profiles ([commit 5a08cf4](https://github.com/googleapis/google-cloud-dotnet/commit/5a08cf49142149d6d38f5a0eea517f362df7eb11))
+
 ## Version 3.19.0, released 2024-08-05
 
 ### New features

apis/apis.json

@@ -1098,7 +1098,7 @@
       "protoPath": "google/bigtable/admin/v2",
       "productName": "Google Cloud Bigtable Administration",
       "productUrl": "https://cloud.google.com/bigtable/",
-      "version": "3.19.0",
+      "version": "3.20.0",
       "commonResourcesConfig": "apis/Google.Cloud.Bigtable.Common.V2/CommonResourcesConfig.json",
       "type": "grpc",
       "description": "Recommended Google client library to access the Google Cloud Bigtable Instance and Table Admin APIs.",