fix: add missing image property to 1ES pipeline pool config

The daily CI build was failing because the pool definition was missing
the required 'image' property. 1ES Pipeline Templates require both
'image' and 'os' to be specified and matching.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: ramsessanchez

.azure-pipelines/daily-ci-build.yml

@@ -21,6 +21,7 @@ extends:
   parameters:
     pool:
       name: Azure-Pipelines-1ESPT-ExDShared
+      image: ubuntu-latest
       os: linux
     sdl:
       sourceAnalysisPool: