Remove reference to deleted file in ms-python.python build script

[JNuss71]

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Description

This PR removes reference to the deleted install_debugpy.py file in the build script for the ms-python.python extension which was causing build failure. The file was deleted in microsoft/vscode-python#23211 since debugpy was removed and the build script in the extension's repo was updated to remove the install_debugpy.py step.

[filiptronicek]

Hey there @JNuss71 👋,
thanks a lot for the contribution, it looks like the build is passing and having built it locally it seems to function as expected.