[clang] [clang-format] Propagate `LeadingEmptyLinesAffected` when joining lines (PR #146761)

[Björn Schäpers via cfe-commits]

https://github.com/HazardyKnusperkeks approved this pull request.

Please wait a few days, or until another approval.

https://github.com/llvm/llvm-project/pull/146761