repo: Update `protoc-gen-validate` links -> bufbuild (#23495)

Signed-off-by: Ryan Northey <ryan@synca.io>

Mirrored from https://github.com/envoyproxy/envoy @ a9aed218c3f650f085fc3ff789e0a59c7f9b8115

API_VERSIONING.md

@@ -63,7 +63,7 @@ experience a backward compatible break on a change. Specifically:
     churn.
 
   * Increasing the strictness of
-    [protoc-gen-validate](https://github.com/envoyproxy/protoc-gen-validate) annotations. Exceptions
+    [protoc-gen-validate](https://github.com/bufbuild/protoc-gen-validate) annotations. Exceptions
     may be granted for scenarios in which these stricter conditions model behavior already implied
     structurally or by documentation.
 

STYLE.md

@@ -184,7 +184,7 @@ metadata. We describe these annotations below by category.
   the field will be promoted to a given `oneof` in the next API major version.
 * `[(udpa.annotations.sensitive) = true]` to denote sensitive fields that
   should be redacted in output such as logging or configuration dumps.
-* [PGV annotations](https://github.com/envoyproxy/protoc-gen-validate) to denote field
+* [PGV annotations](https://github.com/bufbuild/protoc-gen-validate) to denote field
   value constraints.
 
 ### Enum value level

envoy/api/v2/core/grpc_service.proto

@@ -100,7 +100,7 @@ message GrpcService {
       message StsService {
         // URI of the token exchange service that handles token exchange requests.
         // [#comment:TODO(asraa): Add URI validation when implemented. Tracked by
-        // https://github.com/envoyproxy/protoc-gen-validate/issues/303]
+        // https://github.com/bufbuild/protoc-gen-validate/issues/303]
         string token_exchange_service_uri = 1;
 
         // Location of the target service or resource where the client

envoy/config/core/v3/grpc_service.proto

@@ -142,7 +142,7 @@ message GrpcService {
 
         // URI of the token exchange service that handles token exchange requests.
         // [#comment:TODO(asraa): Add URI validation when implemented. Tracked by
-        // https://github.com/envoyproxy/protoc-gen-validate/issues/303]
+        // https://github.com/bufbuild/protoc-gen-validate/issues/303]
         string token_exchange_service_uri = 1;
 
         // Location of the target service or resource where the client