Manually add hashtype in poetry.lock file's metadata.hashes section

Presumably poetry.lock should be autogenerated by Poetry itself and not manually
edited. However there appears to be some bug(s) introduced in recent versions of
Poetry causing it to not install dependencies correctly despite their hashes being
correct (see: python-poetry/poetry#4523). The issue OP's
exact problem was also encountered using the provided poetry.lock file on Poetry
versions 1.1.7 & 1.1.13. This commit works around this issue, till upstream fixes.