Update endpoint (#147)

## Purpose
Update the quickstart bicep to use the correct inbound endpoint

## Does this introduce a breaking change?
<!-- Mark one with an "x". -->
```
[ ] Yes
[x] No
```

## Pull Request Type
What kind of change does this Pull Request introduce?

<!-- Please check the one that applies to this PR using "x". -->
```
[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[x] Documentation content changes
[ ] Other... Please describe:
```

Author: dominicbetts

samples/quickstarts/quickstart.bicep

@@ -70,7 +70,7 @@ resource device 'Microsoft.DeviceRegistry/namespaces/devices@2025-07-01-preview'
         assigned: {}
       }
       inbound: {
-        opcUaEndpointName: {
+        '${opcUaEndpointName}': {
           endpointType: 'Microsoft.OpcUa'
           address: 'opc.tcp://opcplc-000000:50000'
           authentication: {