minor #3922 update fabpot Sphinx extensions version (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
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update fabpot Sphinx extensions version

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets |

As described by @stof in #3918 this pull requests updates the Sphinx extensions to the version that ignores ``*.pyc`` files.

Commits
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62b6185 update fabpot Sphinx extensions version