Disable getting CHANGED_FILES_LIST since it's unused (#8759)

Bug: 382508397

Comment out setting CHANGED_FILES_LIST env variable since it's unused
due to b/382508397.

Author: fayev-g

.github/actions/build/action.yaml

@@ -40,8 +40,9 @@ runs:
           # of the code as if the pull request had been merged into the base branch.
           # Setting fetch-depth to 2 effectively gets a merge commit (i.e. HEAD) and the
           # HEAD commit from the base branch (i.e. HEAD~1).
-          git diff --name-only HEAD~1 HEAD > ${CHANGED_FILES_LIST}
-          cat ${CHANGED_FILES_LIST}
+          # TODO(b/382508397): Disabled for now.
+          # git diff --name-only HEAD~1 HEAD > ${CHANGED_FILES_LIST}
+          # cat ${CHANGED_FILES_LIST}
         shell: bash
       - name: Calculate test targets
         # TODO(b/382508397): Ignore test_root_target until test target listing is dynamic.