text: Title: Hide snapshot report summary if there is nothing to report
  Body: **Is your feature request related to a problem? Please describe.**
  
  <!-- A clear and concise description of what the problem is. Ex. I'm always frustrated when [...] -->
  
  No point in outputting a summary when there is nothing to report
  
  **Describe the solution you'd like**
  
  <!-- A clear and concise description of what you want to happen. -->
  
  Patched this myself by modifying the `pytest_terminal_summary` hook to the following,
  will happily make a PR if this is wanted.
  
  ```py
  with __terminal_color(config):
      lines = terminalreporter.config._syrupy.report.lines
      first = next(lines)
      if first:
          terminalreporter.write_sep("-", gettext("snapshot report summary"))
          terminalreporter.write_line(first)
          for line in lines:
              terminalreporter.write_line(line)
  ```
  
  **Describe alternatives you've considered**
  
  <!-- A clear and concise description of any alternative solutions or features you've considered. -->
  
  **Additional context**
  
  <!-- Add any other context or screenshots about the feature request here. -->
  