fix(fuzzing): correct imports in the intermediate report fuzzing harness

It's theoretically an autogenerated file, however it's checked-in
anyway, plus it's unclear whether there's a protoc-level solution
and investigating that would take inordinate amount of time
compared to this one-liner, given the overall fragility
of the fuzzing setup.

Fixes #5140.

Signed-off-by: Alex T. <[email protected]>

Author: alex-ter