Warning about unused snapshot doesn't need to show all the contents

[deeTEEcee]

Context:

• I have a class with multiple snapshots but often times, I only want to run a single test when I'm troubleshooting an issue or working on new functionality.
• I've possibly mixed in non-snapshot tests with my snapshot tests.

Right now, when you have unused snapshots, it displays the entire contents of that unused snapshot. I think just printing a a list of all those unused methods is good enough.