uhv: fixing path normalizer fuzz test to use proto validation (#24897)

Signed-off-by: Adi Suissa-Peleg <adip@google.com>

Mirrored from https://github.com/envoyproxy/envoy @ ec61d5665ad8423088039f302a658bb9eb106c5b

envoy/extensions/http/header_validators/envoy_default/v3/header_validator.proto

@@ -3,6 +3,7 @@ syntax = "proto3";
 package envoy.extensions.http.header_validators.envoy_default.v3;
 
 import "udpa/annotations/status.proto";
+import "validate/validate.proto";
 
 option java_package = "io.envoyproxy.envoy.extensions.http.header_validators.envoy_default.v3";
 option java_outer_classname = "HeaderValidatorProto";
@@ -107,7 +108,8 @@ message HeaderValidatorConfig {
     // The action to take when request URL path contains escaped slash sequences (``%2F``, ``%2f``, ``%5C`` and ``%5c``).
     // This operation may overwrite the original request URI path and the new path is used for processing of
     // the request by HTTP filters and proxied to the upstream service.
-    PathWithEscapedSlashesAction path_with_escaped_slashes_action = 3;
+    PathWithEscapedSlashesAction path_with_escaped_slashes_action = 3
+        [(validate.rules).enum = {defined_only: true}];
   }
 
   message Http1ProtocolOptions {