chore: remove protoc installation in showcase and update googleapis ci (#13722)

Remove now redundant protoc install step in CIs.

Fixes googleapis/librarian#6720

Author: zhumin8

.github/workflows/showcase.yaml

@@ -127,14 +127,6 @@ jobs:
       - uses: actions/setup-go@40f1582b2485089dde7abd97c1529aa768e1baff # v5
         with:
           go-version: 'stable'
-      - name: Install protoc
-        run: |
-          set -e
-          VERSION="33.2"
-          curl -fsSL --retry 5 --retry-delay 15 -o /tmp/protoc.zip "https://github.com/protocolbuffers/protobuf/releases/download/v$VERSION/protoc-$VERSION-linux-x86_64.zip"
-          cd /usr/local
-          sudo unzip -o /tmp/protoc.zip
-          protoc --version
       - uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5
         with:
           python-version: "3.12"

.github/workflows/update_librarian_googleapis.yaml

@@ -99,15 +99,6 @@ jobs:
         else
           echo "has_changes=true" >> $GITHUB_OUTPUT
         fi
-    - name: Install protoc
-      if: steps.detect_librarian.outputs.has_changes == 'true'
-      run: |
-        set -e
-        VERSION="33.2"
-        curl -fsSL --retry 5 --retry-delay 15 -o /tmp/protoc.zip "https://github.com/protocolbuffers/protobuf/releases/download/v$VERSION/protoc-$VERSION-linux-x86_64.zip"
-        cd /usr/local
-        sudo unzip -o /tmp/protoc.zip
-        protoc --version
     - uses: actions/setup-java@c1e323688fd81a25caa38c78aa6df2d33d3e20d9 # v4
       if: steps.detect_librarian.outputs.has_changes == 'true'
       with: