[ci] Increase memory for BWC steps by moving to n1-standard-32 (#102106) (#102253)

Author: brianseeders

.buildkite/pipelines/periodic.bwc.template.yml

@@ -4,7 +4,7 @@
         agents:
           provider: gcp
           image: family/elasticsearch-ubuntu-2004
-          machineType: custom-32-98304
+          machineType: n1-standard-32
           buildDirectory: /dev/shm/bk
         env:
           BWC_VERSION: $BWC_VERSION