Correctly generate "Prior API version" text

[EronWright]

Updates the generated package description to be correct for 3.x, while also being compatible with 2.x.

In 2.x, the generated code is unchanged. In 3.x:

-Azure REST API version: 2023-02-01. Prior API version in Azure Native 1.x: 2020-11-01.
+Azure REST API version: 2023-02-01. Prior API version in Azure Native 2.x: 2020-11-01.

After merging, we'll cherry-pick to v3 branch and regenerate the SDKs.

Fixes #3866

[github-actions]

Does the PR have any schema changes?

Looking good! No breaking changes found.
No new resources/functions.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 57.26%. Comparing base (58661c2) to head (4b138cb).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
provider/pkg/gen/schema.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3889   +/-   ##
=======================================
  Coverage   57.26%   57.26%           
=======================================
  Files          78       78           
  Lines       12438    12438           
=======================================
  Hits         7122     7122           
  Misses       4769     4769           
  Partials      547      547           

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[thomas11]

nice and simple!

[pulumi-bot]

This PR has been shipped in release v2.85.0.