Update macOS agent

https://devblogs.microsoft.com/devops/hosted-pipelines-image-deprecation/
1 changed files with 2 additions and 2 deletions
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@ -130,10 +130,10 @@ stages:
            artifactType: Container
            parallel: true

-      - job: OSX_10_14
+      - job: OSX_10_15
        displayName: 'OSX'
        pool:
-          vmImage: macOS-11
+          vmImage: macOS-1015
        variables:
        - name: _SignType
          value: none