Revert "Upgrade Linux & Windows CI fleet (#2090)" (#2096)

This reverts commit 9b86972.

Reason: need to adjust quota first

Author: fweikert

buildkite/create_images.py

@@ -101,7 +101,7 @@ def create_instance(instance_name, params):
             instance_name,
             project=params["project"],
             zone=params["zone"],
-            machine_type="c3d-standard-8",
+            machine_type="c2-standard-8",
             network=params.get("network", "default"),
             metadata_from_file=startup_script,
             boot_disk_type="pd-ssd",

buildkite/instances.yml

@@ -14,7 +14,7 @@
 default_vm:
   boot_disk_size: 500GB
   boot_disk_type: pd-ssd
-  machine_type: c3d-standard-30
+  machine_type: c2-standard-30
   network: default
   region: us-central1
   restart-on-failure: False
@@ -26,7 +26,7 @@ default_vm:
   initial_delay: 60
 instance_groups:
   - name: bk-docker
-    count: 200
+    count: 100
     project: bazel-untrusted
     service_account: [email protected]
     image_family: bk-docker
@@ -44,7 +44,7 @@ instance_groups:
     image_family: bk-docker
     metadata_from_file: startup-script=startup-docker-pdssd.sh
   - name: bk-windows
-    count: 60
+    count: 30
     project: bazel-untrusted
     service_account: [email protected]
     image_family: bk-windows