schema: statementType should not have codelist options

[ghost]

#375

Overview

• What does this pull request do?

Fixes a technical issue so compiling a schema for validation is easier.

• How can a reviewer test or examine your changes?

See new standard at https://standard.openownership.org/en/375-fix-statement-type-codelist

Try and compile schema at https://github.com/openownership/lib-cove-bods#updating-schema-files-in-data - note fix described in those instructions is now longer needed

• Who is best placed to review it?

Have already discussed with @rhiaro

Closes issue: #375

Translations

• 👎 I've notified the translation coordinator of any new strings that will need
  translating. See: https://openownership.github.io/bods-dev-handbook/translations.html - Not applicable

Documentation & Release

• I've thought about how and when this needs to be released. See:
  https://openownership.github.io/bods-dev-handbook/standard_releases.html - Think this could be 0.2.1 but not totally sure. Can be 0.3 if not.
• 👍 I've updated the changelog, if necessary. - Not sure it is but done
• 👍 I've added or edited any related documentation. See: https://github.com/openownership/bods-dev-handbook/blob/master/style_guide.md - there is none