fix: python depenency install (#71)

.github/workflows/ci.yml

@@ -47,7 +47,7 @@ jobs:
                 (cd third_party && git clone -b develop --single-branch --depth 1 https://github.com/userver-framework/userver.git)
                 sudo apt update
                 sudo apt install --allow-downgrades -y $(cat third_party/userver/scripts/docs/en/deps/${{matrix.os}}.md | tr '\n' ' ')
-                pip install -r requirements.txt
+                python3 -m pip install -r requirements.txt
 
           - name: Setup ccache
             run: |