fixup! http: support lenient header value validation via insecureHTTPParser

Address review nits from jasnell:
- Clarify that strict regex is the original/default behavior
- Use falsy check for insecureHTTPParser on server

Author: RajeshKumar11

lib/_http_common.js

@@ -256,7 +256,7 @@ function checkIsHttpToken(val) {
   return true;
 }
 
-// Strict header value regex per RFC 7230:
+// Strict header value regex per RFC 7230 (original/default behavior):
 // field-value = *( field-content / obs-fold )
 // field-content = field-vchar [ 1*( SP / HTAB ) field-vchar ]
 // field-vchar = VCHAR / obs-text

lib/_http_outgoing.js

@@ -169,7 +169,7 @@ OutgoingMessage.prototype._isLenientHeaderValidation = function() {
     return this.insecureHTTPParser;
   }
   // ServerResponse can access via req.socket.server
-  if (this.req?.socket?.server?.insecureHTTPParser !== undefined) {
+  if (this.req?.socket?.server?.insecureHTTPParser) {
     return this.req.socket.server.insecureHTTPParser;
   }
   // Fall back to global option