Fix log message

Dependencies

• [2] GTUZLZRH Add an S3-backed binary cache store
• [3] 73YR46NJ hydra-queue-runner: Write directly to a binary cache
• [4] SOB276BA Keep some statistics for the binary cache stores

Change contents

• replacement in src/hydra-queue-runner/binary-cache-store.cc at line 71
  [2.524]→[2.524:559](∅→∅)
  − % info.path % info.narSize
  [2.524]

  [2.559]
  + % narInfo.path % narInfo.narSize