Use pwsh7.2.8 temporarily till 7.2.10 is available (#20911)

Author: BethanyZhou

.azure-pipelines/release-test.yml

@@ -14,7 +14,7 @@ parameters:
 - name: ps7_2
   displayName: PowerShell 7.2.x Version
   type: string
-  default: 7.2.*
+  default: 7.2.8
 - name: ps7_3
   displayName: PowerShell 7.3.x Version
   type: string
@@ -198,4 +198,4 @@ jobs:
     agentPoolName: ${{ variables.macOsAgentPoolName }}
     agentPoolVMImage: ${{ variables.macOsAgentPoolVMImage }}
     psVersion: ${{ parameters.preview_ps }}
-    netCoreVersion: ${{ parameters.netCoreVersion_7 }}
+    netCoreVersion: ${{ parameters.netCoreVersion_7 }}