ci: remove incorrect commit_status_context from pull-requests.json (#12)

Author: pkoutsovasilis

.buildkite/pull-requests.json

@@ -7,7 +7,6 @@
       "allowed_repo_permissions": ["admin", "write"],
       "allowed_list": ["github-actions[bot]"],
       "set_commit_status": true,
-      "commit_status_context": "tk-btf-ci",
       "build_on_commit": true,
       "build_on_comment": true,
       "trigger_comment_regex": "^test",