restore removed installation

I meant to fix this before committing (it was done by Gemini CLI) but
I forgot.

Author: vchudnov-g

.github/workflows/tests.yaml

@@ -348,14 +348,6 @@ jobs:
         run: |
             sudo apt-get update
             sudo apt-get install -y pandoc gcc git
-      - name: Install protoc.
-        run: |
-            sudo mkdir -p /usr/src/protoc/
-            sudo chown -R ${USER} /usr/src/
-            curl --location https://github.com/google/protobuf/releases/download/v${PROTOC_VERSION}/protoc-${PROTOC_VERSION}-linux-x86_64.zip --output /usr/src/protoc/protoc-${PROTOC_VERSION}.zip
-            cd /usr/src/protoc/
-            unzip protoc-${PROTOC_VERSION}.zip
-            sudo ln -s /usr/src/protoc/bin/protoc /usr/local/bin/protoc
       - name: Install nox.
         run: |
             python -m pip install nox

noxfile.py

@@ -171,6 +171,8 @@ def fragment(session, use_ads_templates=False):
         "pytest-asyncio",
         "grpcio-tools",
     )
+    session.install("-e", ".")
+
     # The specific failure is `Plugin output is unparseable`
     if session.python in ("3.9", "3.10"):
         session.install("google-api-core<2.28")