dt-bindings: clock: qcom: gcc-sm8450: drop test clock

The test clock apparently it's not used by anyone upstream. Remove it.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20221228185237.3111988-8-dmitry.baryshkov@linaro.org