Do not create remove_bad_files.sh

[fantazio]

Instead of creating the script and suggesting to run it, the following error message is printed after scanning the files and before the reports (example appearing on Goblint):

*** WARNING: 14 files cannot be read. Run with `--verbose` for more details.

When running with --verbose, the errors are printed on stderr during the scan, along with the Scanning messages,
with messages prefixed with "ERROR: ". On Goblint again, part of the output is:

Scanning interface from _build/default/tests/util/.yamlWitnessStrip.eobjs/byte/dune_site__Dune_site_data.cmt
ERROR: _build/default/tests/util/.yamlWitnessStrip.eobjs/byte/dune_site__Dune_site_data.cmt: missing cmi_sign
Scanning implementation from _build/default/tests/util/.yamlWitnessStrip.eobjs/byte/dune_site__Dune_site_data.cmt
Scanning interface from _build/default/tests/util/.yamlWitnessStrip.eobjs/byte/dune__exe__YamlWitnessStripDiff.cmti
Scanning implementation from _build/default/tests/util/.yamlWitnessStrip.eobjs/byte/dune__exe__YamlWitnessStripDiff.cmt

Also update the error message for cmt read failures to a more informative one

-<cmt_filepath>: error reading file
+<cmt_filepath>: invalid magic number. Tip: the file must be compiled with the same OCaml version as the dead_code_analyzer.

Fix issue #85.