Datatype OpenGraphData is exported but not used

[MV-GH]

This should be removed.

[dessalines]

Its harmless, and its auto-generated like this because in the back end we're using flatten so as not to have a breaking change. But it is its own distinct type.

pub struct LinkMetadata {
  #[serde(flatten)]
  pub opengraph_data: OpenGraphData,
  pub content_type: Option<String>,
}