Revert "Install npm-packages before running polygerrit tests"

Installing the packages from package.json results in a broken
build on stable-* branches.

This reverts commit 735b36277f03884216237b5f05b63ea7334d034b.

Change-Id: Icf7a108d120c313ca9f29e8d4d256454b65cccec
diff --git a/jenkins/gerrit-bazel-test.sh b/jenkins/gerrit-bazel-test.sh
index 9b11f38..a7d5563 100755
--- a/jenkins/gerrit-bazel-test.sh
+++ b/jenkins/gerrit-bazel-test.sh
@@ -3,9 +3,6 @@
 cd gerrit
 . set-java.sh 8
 
-echo 'Installing required npm packages...'
-yarn install --offline || yarn install
-
 export BAZEL_OPTS="$BAZEL_OPTS --spawn_strategy=standalone --genrule_strategy=standalone \
                    --test_output errors \
                    --test_summary detailed --flaky_test_attempts 3 \
diff --git a/jenkins/gerrit-bazel-verifier-test.sh b/jenkins/gerrit-bazel-verifier-test.sh
index 2bea6fb..d74bf34 100755
--- a/jenkins/gerrit-bazel-verifier-test.sh
+++ b/jenkins/gerrit-bazel-verifier-test.sh
@@ -32,9 +32,6 @@
 
 if [[ "$MODE" == *"polygerrit"* ]]
 then
-  echo 'Installing required npm packages...'
-  yarn install --offline || yarn install
-
   if [ -z "$DISPLAY" ]
   then
     echo 'Not running local tests because env var "DISPLAY" is not set.'