ci(docs): remove d2 install step

.github/workflows/docs.yml

@@ -27,9 +27,6 @@ jobs:
       - name: Install pandoc
         run: sudo apt-get update && sudo apt-get install -y pandoc
 
-      - name: Install d2
-        run: curl -fsSL https://d2lang.com/install.sh | sh -s -- --version v0.7.1
-
       - name: Build site
         run: make docs