Revert "Enhance cache-dependency-path handling to support files outside the workspace root"

[aparnajyothi-y]

This reverts commit 1264885.

Description:
Reverts PR #1128. That change copied a file from the composite action into the workspace to support composite actions, but we’ve decided to implement this capability at the actions/toolkit level instead (see actions/toolkit#1035) for a more consistent and scalable solution.

[Copilot]

Pull Request Overview

This PR reverts commit 1264885 which enhanced cache-dependency-path handling to support files outside the workspace. The functionality is being reimplemented at the actions/toolkit level for better consistency across actions.

Key changes:

• Removes complex file copying logic from the cacheDependencies function
• Eliminates associated test coverage for the removed functionality
• Removes documentation note about support for files outside workspace

Reviewed Changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 1 comment.

File	Description
src/setup-python.ts	Reverts cacheDependencies function to simpler implementation without file copying logic
docs/advanced-usage.md	Removes documentation note about cache-dependency-path supporting files outside workspace
tests/setup-python.test.ts	Removes all test cases for the reverted file copying functionality
.github/workflows/test-pypy.yml	Adds windows-2019 to test matrix (unrelated change)

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