gci: Switch docs and CI builder to use poetry

.github/scripts/build.sh

@@ -21,28 +21,9 @@ export VALGRIND=${VALGRIND:-0}
 export FUZZING=${FUZZING:-0}
 export LIGHTNINGD_POSTGRES_NO_VACUUM=1
 
-pip3 install --user -U \
-     -r requirements.lock
-
-timeout 60 pip3 install --user \
-     --use-feature=in-tree-build \
-     ./contrib/pyln-client \
-     ./contrib/pyln-proto \
-     ./contrib/pyln-testing
-
-# Install utilities that aren't dependencies, but make
-# running tests easier/feasible on CI (and pytest which
-# keeps breaking the rerunfailures plugin).
-pip3 install --user \
-     blinker \
-     flake8 \
-     flaky \
-     mako \
-     pytest-sentry \
-     pytest-test-groups==1.0.3 \
-     pytest-custom-exit-code==0.3.0 \
-     pytest-timeout \
-     pytest-json-report
+pip3 install --user poetry
+poetry config virtualenvs.create false --local
+poetry install
 
 git clone https://github.com/lightningnetwork/lightning-rfc.git ../lightning-rfc
 git submodule update --init --recursive