test/lib/mutation_diff: s/colordiff/diff/
test/lib/mutation_diff: s/colordiff/diff/

Colordiff is problematic when writing the diff into a file for later
examination. Use regular diff instead. One can still get syntax
highlighting by writing the output into `.diff` file (which most editors
will recognize).

Signed-off-by: Botond Dénes <a584fa4d75a0a85d721f44fb6e06315a2853b0b6@scylladb.com>
Message-Id: <20220407080944.324108-1-a584fa4d75a0a85d721f44fb6e06315a2853b0b6@scylladb.com>

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla