Updated parser readme after last refactoring. [skip-ci]

README.parsers.md

@@ -51,12 +51,12 @@ import sys
 from nomad.cli.parse import parse, normalize_all
 
 # match and run the parser
-backend = parse(sys.argv[1])
+archive = parse(sys.argv[1])
 # run all normalizers
-normalize_all(backend)
+normalize_all(archive)
 
 # get the 'main section' section_run as a metainfo object
-section_run = backend.resource.contents[0].section_run[0]
+section_run = archive.section_run[0]
 
 # get the same data as JSON serializable Python dict
 python_dict = section_run.m_to_dict()