fix(gatsby-plugin-netlify): cast status to string (#18726)

* fix(gatsby-plugin-netlify): cast `status` to string

* Update create-redirects.js

Author: visualfanatic

Diff for: packages/gatsby-plugin-netlify/src/create-redirects.js

@@ -26,9 +26,9 @@ export default async function writeRedirectsFile(
     } = redirect
 
     let status = isPermanent ? `301` : `302`
-    if (statusCode) status = statusCode
+    if (statusCode) status = String(statusCode)
 
-    if (force) status = status.concat(`!`)
+    if (force) status = `${status}!`
 
     // The order of the first 3 parameters is significant.
     // The order for rest params (key-value pairs) is arbitrary.