python3-pytest: Remove dependency on python3-toml

Since version 7.2.0 [1], pytest uses the "batteries included" tomllib
module for parsing pyproject.toml configuration files [2]. It is
therefore no longer necessary to have python3-toml in RDEPENDS.

[1] https://docs.pytest.org/en/latest/changelog.html#pytest-7-2-0-2022-10-23
[2] https://github.com/pytest-dev/pytest/pull/9741



Signed-off-by: Arnout Vandecappelle <arnout@mind.be>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>