Revert "Add flask to the test deps"

This reverts commit 99b8fe7.

.github/workflows/ci.yml

@@ -22,7 +22,7 @@ jobs:
       - name: Install ZanzoCam
         run: |
           sudo apt-get install language-pack-it wireless-tools
-          pip install Pillow requests piexif pytest pytest-coverage pytest-subprocess freezegun coveralls flask
+          pip install Pillow requests piexif pytest pytest-coverage pytest-subprocess freezegun coveralls
           pip install --no-deps -e .
 
       - name: Unit tests