Revert "Migrate eng/common (except job-matrix) to Ubuntu 22.04 (#5005)" for perf.yml (Azure#33321)

This reverts commit 81c78afd563a32c224eb45b0cf864078d55b68eb.

Co-authored-by: Mike Harder <mharder@microsoft.com>

Author: azure-sdk

eng/common/pipelines/templates/jobs/perf.yml

@@ -4,10 +4,10 @@ parameters:
   default: 'Perf'
 - name: LinuxPool
   type: string
-  default: azsdk-pool-mms-ubuntu-2204-perf
+  default: 'azsdk-pool-mms-ubuntu-2004-perf'
 - name: LinuxVmImage
   type: string
-  default: MMSUbuntu22.04
+  default: 'MMSUbuntu20.04'
 - name: WindowsPool
   type: string
   default: 'azsdk-pool-mms-win-2019-perf'