Changing customConfig from optional to required

[q3blend]

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[fearthecowboy]

FYI -this will cause a binary breaking change in the generated SDK (and perhaps a order change in the method parameters).

I'm assuming this is OK with you?

[q3blend]

Yes, this is Ok with me.

[AutorestCI]

Was unable to find SDK Azure/azure-sdk-for-python PR for this closed PR.

[AutorestCI]

No modification for AutorestCI/azure-sdk-for-python

[AutorestCI]

No modification for AutorestCI/azure-sdk-for-ruby

[AutorestCI]

No modification for AutorestCI/azure-sdk-for-python

[AutorestCI]

No modification for AutorestCI/azure-sdk-for-ruby