update container to immediateContainer

[odscjen]

addresses part of open-contracting/standard#1343

[odscjen]

@jpmckinney test_csv.py is looking specifically for "container.csv" at line 93

@pytest.mark.skipif(repo_name in ('european-union-support',), reason='not a codelist')
def test_codelist():
    """
    Ensures all codelists files are valid against codelist-schema.json.
    """
    exceptions = {
        'currency.csv': "'Description' is a required property",
        'language.csv': "'Description' is a required property",
        'mediaType.csv': "'Description' is a required property",
        # ocds_countryCode_extension
        'country.csv': "'Description' is a required property",
        # ocds_coveredBy_extension
        'coveredBy.csv': "'Description' is a required property",
        # ocds_medicine_extension
        'administrationRoute.csv': "'Description' is a required property",
        'container.csv': "None is not of type 'string'",
        'dosageForm.csv': "None is not of type 'string'",
    }

but this PR changes the name of this codelist to "immediateContainer.csv", I think that's what's causing this test to fail here.

[jpmckinney]

Thanks! I've updated the test.

[jpmckinney]

I added a changelog as a separate commit.