[QUESTION] Missing Σ (sigma) symbol in Unit 4 "Gradient Ascent and the Policy-gradient Theorem"

I am referring to [this section](https://huggingface.co/learn/deep-rl-course/unit4/policy-gradient#gradient-ascent-and-the-policy-gradient-theorem) and specifically to this image:


Shouldn't there be a Σ (sigma) symbol right before the gradient operator? For reference, here is how the Policy-gradient Theorem is derived in OpenAI's ["Spinning Up" course](https://spinningup.openai.com/en/latest/spinningup/rl_intro3.html#deriving-the-simplest-policy-gradient).