ci: use Cython from pip

.github/workflows/ccpp.yml

@@ -30,10 +30,10 @@ jobs:
     - name: Dependencies
       run: |
         sudo apt install ninja-build libncurses5-dev libreadline-dev nettle-dev libasio-dev \
-        libgnutls28-dev libuv1-dev cython3 python3-dev python3-setuptools python3-pip \
+        libgnutls28-dev libuv1-dev python3-dev python3-setuptools python3-pip \
         libcppunit-dev libjsoncpp-dev libfmt-dev libhttp-parser-dev libmsgpack-dev libargon2-0-dev
-    - name: Meson
-      run: sudo pip3 install meson
+    - name: Python dependencies
+      run: sudo pip3 install meson Cython
     - name: Configure
       run: meson setup build .
     - name: Build