Update recipe to 4.2.0

[dhirschfeld]

Checklist

• Used a fork of the feedstock to propose changes
• Bumped the build number (if the version is unchanged)
• Reset the build number to 0 (if the version changed)
• Re-rendered with the latest conda-smithy (Use the phrase @conda-forge-admin, please rerender in a comment in this PR for automated rerendering)
• Ensured the license file is being packaged.

[conda-forge-linter]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipe) and found it was in an excellent condition.

[dhirschfeld]

@conda-forge-admin, please rerender

[dhirschfeld]

Expected exception:

conda.exceptions.ResolvePackageNotFound: 
  - azure-keyvault-keys~=4.2.0
  - azure-keyvault-certificates~=4.2.0
  - azure-keyvault-secrets~=4.2.0

Depends on:

• Add azure-keyvault-secrets staged-recipes#12743
• Add azure-keyvault-keys staged-recipes#12745
• Add azure-keyvault-certificates staged-recipes#12746

[dhirschfeld]

ping @conda-forge/core - this PR fixes up this package which has now been split into the 3 packages listed above.

https://github.com/Azure/azure-sdk-for-python/tree/master/sdk/keyvault/azure-keyvault