chore(main): release gapic-common 0.21.0 (#1015)

Author: release-please[bot]

.release-please-manifest.json

@@ -1,4 +1,4 @@
 {
   "gapic": "0.1.0",
-  "gapic-common": "0.20.0"
+  "gapic-common": "0.21.0"
 }

gapic-common/CHANGELOG.md

@@ -1,5 +1,12 @@
 # Release History
 
+### 0.21.0 (2023-12-13)
+
+#### Features
+
+* Drop support for Ruby 2.6 ([#1009](https://github.com/googleapis/gapic-generator-ruby/issues/1009)) 
+* Honor universe domain in stubs ([#1008](https://github.com/googleapis/gapic-generator-ruby/issues/1008)) 
+
 ### 0.20.0 (2023-08-31)
 
 #### Features

gapic-common/lib/gapic/common/version.rb

@@ -14,6 +14,6 @@
 
 module Gapic
   module Common
-    VERSION = "0.20.0".freeze
+    VERSION = "0.21.0".freeze
   end
 end