don't set package pretty_version

[dimbleby]

The pretty_version on the Package is pointless, it can always just be taken from the regular version's .text.

This is the only place in the codebase that sets it; and clearly it's not doing anything useful.

This is a prelude to corresponding tidying in poetry-core

[dimbleby]

test failure looks spurious:

      � Installing cleo (0.6.5)
  +   � Installing tomlkit (0.5.5)
      � Installing pendulum (1.4.4)
  -   � Installing tomlkit (0.5.5)
      � Installing demo (0.1.2 9cf87a2)

hard to believe that this MR changes that but only on Windows 3.10

(also this is clearly an over-specified test, though I'm not proposing to do anything about that since I assume the problem will go away on retry)

[github-actions]

This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.