Bump third_party/pigweed/repo from `9e4bfb9` to `18e1276` #3135

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1 error and 6 warnings

Process completed with exit code 1.

Failed to save: "/usr/bin/tar" failed with error: The process '/usr/bin/tar' failed with exit code 2

`pre` execution is not supported for local action from './.github/actions/bootstrap-cache'

`pre` execution is not supported for local action from './.github/actions/checkout-submodules'

No files were found with the provided path: /tmp/cirque_test_output/. No artifacts will be uploaded.

`pre` execution is not supported for local action from './.github/actions/checkout-submodules'

`pre` execution is not supported for local action from './.github/actions/bootstrap-cache'