51degreesRtdProvider: update doc

- clarified the free availability of the api
- improved configuration description

dev-docs/modules/51DegreesRtdProvider.md

@@ -123,8 +123,8 @@ pbjs.setConfig({
                 name: '51Degrees',
                 waitForIt: true, // should be true, otherwise the auctionDelay will be ignored
                 params: {
-                    // Get your resource key from https://configure.51degrees.com/tWrhNfY6 to connect to cloud.51degrees.com
                     resourceKey: '<YOUR_RESOURCE_KEY>',
+                    // Get your resource key from https://configure.51degrees.com/HNZ75HT1
                     // alternatively, you can use the on-premise version of the 51Degrees service and connect to your chosen end point
                     // onPremiseJSUrl: 'https://localhost/51Degrees.core.js'
                 },