Fix false positives in codespell CI and fix reported typos

- Don't install codespell when building offline docs
  as it's not needed in that workflow.

.github/workflows/build_offline_docs.yml

@@ -23,7 +23,6 @@ jobs:
       - name: Install dependencies
         run: |
           sudo pip3 install -r requirements.txt
-          sudo pip3 install codespell
           sudo apt update
           sudo apt install parallel libwebp7