chore(deps): update gapic-generator-java-bom.version to v2.21.0 (#1937)

* chore(deps): update gapic-generator-java-bom.version to v2.21.0

* chore(deps): update protobuf version used to compile test protos to 3.23.2

* test: update golden files with expected copyright year changes

---------

Co-authored-by: Renovate Bot <bot@renovateapp.com>

spring-cloud-generator/pom.xml

@@ -15,10 +15,10 @@
     <description>Spring Code Generator for Google Cloud</description>
 
     <properties>
-        <gapic-generator-java-bom.version>2.20.1</gapic-generator-java-bom.version>
+        <gapic-generator-java-bom.version>2.21.0</gapic-generator-java-bom.version>
         <!-- [gapic-test]: protobuf.version for compiling protos used in unit testing
              this should be consistent with version in gapic-generator-java-bom -->
-        <protobuf.version>3.21.12</protobuf.version>
+        <protobuf.version>3.23.2</protobuf.version>
     </properties>
 
     <dependencyManagement>

spring-cloud-generator/src/test/java/com/google/cloud/generator/spring/composer/goldens/EchoSpringAutoConfigurationFull.golden

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022 Google LLC
+ * Copyright 2023 Google LLC
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.

spring-cloud-generator/src/test/java/com/google/cloud/generator/spring/composer/goldens/EchoSpringPropertiesFull.golden

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022 Google LLC
+ * Copyright 2023 Google LLC
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.

spring-cloud-generator/src/test/java/com/google/cloud/generator/spring/composer/goldens/SpringPackageInfoFull.golden

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022 Google LLC
+ * Copyright 2023 Google LLC
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.