Change test node to linux-x86_64.

Docker is now installed in all VM nodes, and docker nodes are removed.

Change-Id: I1e811d7ea837e94e1011f541cc16429025b15c7a
diff --git a/scripts/ci/bazel-toolchains.json b/scripts/ci/bazel-toolchains.json
index b05b16b..1e866c8 100644
--- a/scripts/ci/bazel-toolchains.json
+++ b/scripts/ci/bazel-toolchains.json
@@ -1,6 +1,6 @@
 [
   {
-    "node": "docker",
+    "node": "linux-x86_64",
     "parameters": {
       "build_opts": [
         "--verbose_failures"