`clap_man` doesn't consider an option required when its arg group is required

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Please complete the following tasks

• I have searched the discussions
• I have searched the existing issues

Rust Version

rustc 1.55.0 (c8dfcfe04 2021-09-06)

Clap Version

v3.0.6

Minimal reproducible code

N/A

Steps to reproduce the bug with the above code

N/A

Actual Behaviour

It should show as required

Expected Behaviour

It shows as optional

Additional Context

Split out of #3174

Debug Output

No response