docs: Use SetProviderAndWait in README example (#333)

Signed-off-by: Nicholas Thomson <[email protected]>

Author: RedbackThomson

README.md

@@ -67,7 +67,7 @@ import (
 
 func main() {
     // Register your feature flag provider
-    openfeature.SetProvider(openfeature.NoopProvider{})
+    openfeature.SetProviderAndWait(openfeature.NoopProvider{})
     // Create a new client
     client := openfeature.NewClient("app")
     // Evaluate your feature flag
@@ -81,7 +81,7 @@ func main() {
 }
 ```
 
-Try this example in the [Go Playground](https://go.dev/play/p/k0wqE8LPdR_X).
+Try this example in the [Go Playground](https://go.dev/play/p/fSSK8s42hA2).
 
 ### API Reference