doc: requirements: disallow breathe 4.33.0

Sphinx 4.33.0 introduces Graphviz support, but the Graphviz
configuration value names clash with the Sphinx built-in Graphviz
extension.

Issue: https://github.com/michaeljones/breathe/issues/803



Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>