Add RemoveField action proto for ProtoApiScrubber filter

api/envoy/extensions/filters/http/proto_api_scrubber/v3/matcher_actions.proto

@@ -0,0 +1,21 @@
+syntax = "proto3";
+
+package envoy.extensions.filters.http.proto_api_scrubber.v3;
+
+import "xds/annotations/v3/status.proto";
+
+import "udpa/annotations/status.proto";
+
+option java_package = "io.envoyproxy.envoy.extensions.filters.http.proto_api_scrubber.v3";
+option java_outer_classname = "MatcherActionsProto";
+option java_multiple_files = true;
+option go_package = "github.com/envoyproxy/go-control-plane/envoy/extensions/filters/http/proto_api_scrubber/v3;proto_api_scrubberv3";
+option (udpa.annotations.file_status).package_version_status = ACTIVE;
+option (xds.annotations.v3.file_status).work_in_progress = true;
+
+// [#protodoc-title: Proto API Scrubber Matcher Actions]
+
+// Specifies an :ref:`Unified Matcher API <envoy_v3_api_msg_.xds.type.matcher.v3.Matcher>` action to remove a field.
+// This actual action needs to be implemented by the filter using it.
+message RemoveFieldAction {
+}