[md2orchestra] NumInGroup field erroneously inherits group scenario

[donmendelson]

When copying a group from a reference file, a NumInGroup field inherits the group scenario. It should only have a non-base scenario if the NumInGroup has an explicit scenario in markdown.

[kleihan]

Tested successfully with FIX Latest as reference file and SecAltIDGrp as well as one of its fields defined as a scenario (removed annotations elements from XML snippets):

### Group SecAltIDGrp scenario TEST

| Name                | Tag | Presence | Scenario
|---------------------|----:|----------|---------
| NoSecurityAltID     | 454 | optional |
| SecurityAltID       | 455 | optional |
| SecurityAltIDSource | 456 | optional | TEST

        <fixr:group id="2071" name="SecAltIDGrp" scenario="TEST">
            <fixr:numInGroup id="454"/>
            <fixr:fieldRef id="455"/>
            <fixr:fieldRef id="456" scenario="TEST"/>
        </fixr:group>

        <fixr:field type="NumInGroup" id="454" name="NoSecurityAltID"/>
        <fixr:field type="String" discriminatorId="456" id="455" name="SecurityAltID"/>
        <fixr:field type="SecurityIDSourceCodeSet" id="456" name="SecurityAltIDSource" scenario="TEST"/>