The sphinx-rtd-theme package is not yet compatible with sphinx 7.
The 1.2.2 version of the theme pins sphinx to <7 which does work and
allows us to have a transitive pin on sphinx that will be auto-removed
once sphinx-rtd-theme is updated to work with sphinx 7 and released.
Change-Id: Ib6771ebe5a30892ee16499f2434fe48e018e877c
92bbf8a165