Submodule GitExtensionsDoc updated.

Submodule GitExtensionsDoc:
    > 39a232c - In version 2.45 settings are still stored in registry.
    > 7a3ee01 - Chapter 2 Updated
    > 9f1dbdb - Add logo to RTD and release # to TOC
    > d02d225 - Add Wiki details
    > a120c4e - Fix incomplete sentence.
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