Testing: Remove unnecessary encode to utf-8; rucio#6538

UTF-8 is the default encoding in Python,
so there is no need to call encode when UTF-8 is the desired encoding.
Instead, use a bytes literal.

See also:
- https://docs.astral.sh/ruff/rules/unnecessary-encode-utf8/

tests/test_dumper.py

@@ -83,7 +83,7 @@ def test_smart_open_for_bz2_file():
     fd, path = tempfile.mkstemp()
     comp = bz2.BZ2Compressor()
     with os.fdopen(fd, 'wb') as f:
-        f.write(comp.compress('abcdef'.encode()))
+        f.write(comp.compress(b'abcdef'))
         f.write(comp.flush())
     assert not isinstance(dumper.smart_open(path), bz2.BZ2File)
     os.unlink(path)