Update knex Node integration (#12223)

Sentry.knexIntegration is not a constructor (only a void function can be called with the 'new' keyword).

Author: Neamar

docs/platforms/javascript/common/configuration/integrations/knex.mdx

@@ -34,7 +34,7 @@ The `knexIntegration` adds instrumentation for the `knex` library to capture spa
 
 ```javascript
 Sentry.init({
-  integrations: [new Sentry.knexIntegration()],
+  integrations: [Sentry.knexIntegration()],
 });
 ```