ci: remove obsolete local google-http-java-client snapshot checkout steps from showcase workflow

Author: lqiu96

.github/workflows/showcase.yaml

@@ -40,18 +40,6 @@ jobs:
           java-version: 11
           distribution: temurin
           cache: maven
-      - name: Checkout google-http-java-client (pqc-support-conscrypt branch)
-        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
-        with:
-          repository: googleapis/google-http-java-client
-          ref: pqc-support-conscrypt
-          path: google-http-java-client
-          persist-credentials: false
-      - name: Build and install local google-http-java-client snapshot
-        working-directory: google-http-java-client
-        run: |
-          mvn install -DskipTests -Dmaven.javadoc.skip=true -Dclirr.skip=true -B -ntp
-          cd .. && rm -rf google-http-java-client
       - name: Install all modules using Java 11
         shell: bash
         run: .kokoro/build.sh
@@ -132,18 +120,6 @@ jobs:
           java-version: ${{ matrix.java }}
           distribution: temurin
       - run: mvn -version
-      - name: Checkout google-http-java-client (pqc-support-conscrypt branch)
-        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
-        with:
-          repository: googleapis/google-http-java-client
-          ref: pqc-support-conscrypt
-          path: google-http-java-client
-          persist-credentials: false
-      - name: Build and install local google-http-java-client snapshot
-        working-directory: google-http-java-client
-        run: |
-          mvn install -DskipTests -Dmaven.javadoc.skip=true -Dclirr.skip=true -B -ntp
-          cd .. && rm -rf google-http-java-client
       - name: Install Maven modules
         shell: bash
         run: .kokoro/build.sh
@@ -253,18 +229,6 @@ jobs:
           java-version: 17
           distribution: temurin
           cache: maven
-      - name: Checkout google-http-java-client (pqc-support-conscrypt branch)
-        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
-        with:
-          repository: googleapis/google-http-java-client
-          ref: pqc-support-conscrypt
-          path: google-http-java-client
-          persist-credentials: false
-      - name: Build and install local google-http-java-client snapshot
-        working-directory: google-http-java-client
-        run: |
-          mvn install -DskipTests -Dmaven.javadoc.skip=true -Dclirr.skip=true -B -ntp
-          cd .. && rm -rf google-http-java-client
       - name: Install Maven modules
         shell: bash
         run: .kokoro/build.sh