There are two ways to finish this up.
If you choose to use only dynamic lighting this will give the effect quite easily since dynamic lights do not have any bounce light (GI). So any fully shadowed part will appear black automatically.
If you just want to control the amount of GI that was produced and baked with the static lighting then you can simply control this with the Post Process Volume. You can go under the Global Illumination setting and set the Indirect Lighting Intensity to 0 or a lower value that meets your needs. Setting it to 0 will make any baked GI completely black like it would be from a direct shadow of a dynamic light.