[2.7] bpo-24746: Avoid stripping trailing whitespace in doctest fancy diff (#11482)

[2.7] bpo-24746: Avoid stripping trailing whitespace in doctest fancy diff (#11482)

* bpo-24746: Avoid stripping trailing whitespace in doctest fancy diff

* [2.7] bpo-24746: Avoid stripping trailing whitespace in doctest fancy diff (GH-10639).
(cherry picked from commit cbb16459934eaf29c7c7d362939cd05550b2f21f)

Co-authored-by: Sanyam Khurana <8039608+CuriousLearner@users.noreply.github.com>