Revert "[fuzzer] Use puts() rather than printf() in CopyFileToErr()"

This reverts commit 03aa02adb03c928ae4ec9d139b303348f81861c9.

Reverting due to bot failures:
https://lab.llvm.org/buildbot/#/builders/247/builds/2653

GitOrigin-RevId: d02ff3d578312f4924b7d3926666ea454239bf25
2 files changed