Default to adding the {{copy}} Killercoda action to all fenced code blocks

[jdbaldry]

No need to use the copy directive, the default is copyable.
The exec directive overrides the {{copy}} action if its used.

Signed-off-by: Jack Baldry [email protected]

[Jayclifford345]

Tested and working!

```alloy
 otelcol.receiver.otlp "default" {
   http {}
   grpc {}

   output {
     logs    = [otelcol.processor.batch.default.input]
   }
 }
```{{copy}}

LGTM!!