Update 0_webui.yml

Author: DilumAluthge

.buildkite/pipelines/main/0_webui.yml

@@ -21,4 +21,4 @@ steps:
           # verifies the treehash of the pipeline itself and the inputs listed in `inputs`
           signed_pipelines:
             - pipeline: .buildkite/pipelines/main/misc/signed_pipeline_test.yml
-              signature: "U2FsdGVkX18ZrMlORSIi0TvW99eZ3JyUEhntMyXjrOSJ9jAtUohgHc8+dMnWUc6qWjYt8k63wfPrth33SGWDiF814Bm1W5Zk3+R6HgVu6UCrQEI5sLm+SJPbrvET+Jkn"
+              signature_file: .buildkite/pipelines/main/misc/signed_pipeline_test.yml.signature