chore: remove libraries-bom-protobuf3 folder (#7495)

Author: blakeli0

README.md

@@ -31,7 +31,7 @@ To use it in Maven, add the following to your POM:
 When you use the Libraries BOM, you don't specify individual library versions
 and your application runs on a consistent set of the dependencies.
 
-If you encounter compatibility issues with protobuf-java 4.x, update your codebase and dependencies to ensure compatibility, see [release notes of libraries-bom v26.50.0](https://github.com/googleapis/java-cloud-bom/releases/tag/v26.50.0) for potential compatibility issues. If this is not feasible, use `com.google.cloud:libraries-bom-protobuf3` as a workaround. `com.google.cloud:libraries-bom-protobuf3` includes the same client libraries and library versions as libraries-bom.
+If you encounter compatibility issues with protobuf-java 4.x, update your codebase and dependencies to ensure compatibility, see [release notes of libraries-bom v26.50.0](https://github.com/googleapis/java-cloud-bom/releases/tag/v26.50.0) for potential compatibility issues.
 
 ## Libraries in Scope
 

libraries-bom-protobuf3/pom.xml

@@ -174,7 +174,7 @@ private void printKeyCoreLibraryDependencies(Bom bom) {
         .append("\n")
         .append("\n");
     report
-        .append("If you encounter compatibility issues with protobuf-java 4.x, please update your codebase and dependencies to ensure compatibility. If this is not feasible, use libraries-bom-protobuf3 as a workaround. libraries-bom-protobuf3 includes the same client libraries and library versions as libraries-bom.")
+        .append("If you encounter compatibility issues with protobuf-java 4.x, please update your codebase and dependencies to ensure compatibility.")
         .append("\n");
   }