Move MapOpenApi() Inside the IsDevelopment() block for consistency with templates and other docs

The default template with .NET 9 has MapOpenApi() inside the IsDevelopment block. Many examples on MS Learn also have it inside due to limit information exposure. 

Move inside to minimize potential for confusion to devs.

Author: davepcallan

aspnetcore/fundamentals/openapi/samples/9.x/WebMinOpenApi/Program.cs

@@ -279,9 +279,10 @@ public class Body {
 
 var app = builder.Build();
 
-app.MapOpenApi();
 if (app.Environment.IsDevelopment())
 {
+    app.MapOpenApi();
+    
     app.UseSwaggerUI(options =>
     {
         options.SwaggerEndpoint("/openapi/v1.json", "v1");