[Storage] rename SKUs to Skus

[JasonYang-MSFT]

Description

Fixed bad names in swagger for python SDK, which affect other SDKs.
Since 7.0.0 haven't released yet, this will not break current experience for customers.

Azure/azure-rest-api-specs#1650

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[shahabhijeet]

Please add < PackageReleaseNotes > and add Release notes in .csproj. This helps in knowing what is included in the nuget package.
I would recommend to use < ![CDATA and then format your Release notes

[JasonYang-MSFT]

Changelog added, it should be available once this pr is merged.

[shahabhijeet]

This property has to be part of a propertygroup

[JasonYang-MSFT]

Updated.