[tests] dune: fix test directory 'metrics'

tests/metrics/func_ptr.c

tests/metrics/libc.c

tests/metrics/oracle/func_ptr.0.res.oracle

tests/metrics/oracle/func_ptr.1.res.oracle

tests/metrics/oracle/reach.res.oracle

tests/metrics/oracle/referenced-by-acsl.res.oracle

tests/metrics/reach.c

tests/metrics/referenced-by-acsl.c

tests/metrics/unreachable.c

tests/metrics/used-files.i