[Github Actions] Remove --break-system-packages flag (#570)

```
no such option: --break-system-packages
Error: Process completed with exit code 2.
```

not sure why I had to insert it yesterday :/
#566

.github/steps/prepare_minimal_ubuntu_image/action.yml

@@ -6,4 +6,4 @@ runs:
   - name: Install dependencies
     shell: bash
     run: |
-      python3 -m pip install --break-system-packages fire pyyaml jsonpath_ng joblib
+      python3 -m pip install fire pyyaml jsonpath_ng joblib

.github/workflows/build_docs.yml

@@ -22,7 +22,7 @@ jobs:
 
       - name: Install requirements
         run: |
-          python3 -m pip install --break-system-packages -r docs/requirements.txt
+          python3 -m pip install -r docs/requirements.txt
 
       - name: Render the docs
         run: |