text: Title: Remove assertion call syntax
  Body: **Is your feature request related to a problem? Please describe.**
  
  One of the project's motivations is to provide a uniform, idiomatic way to assert snapshots. We're keeping `snapshot.assert_match` for backwards compatibility with snapshottest for the moment, however no one uses the `snapshot(actual)` syntax. It's a remnant of testing out different approaches.
  
  **Describe the solution you'd like**
  
  Remove the snapshot call syntax: https://github.com/tophat/syrupy/blob/7cc40476556cbb7ddb3f60bab81668341550a742/src/syrupy/assertion.py#L123