Add deprecation warning for `treat_symbols_as_metadata_keys_with_true_values`.
Created by: tundal45
Add a custom message to notify users that this is now the default behavior.
I wanted to add a spec that tested the message but when I was looking at the corresponding spec, I could not figure out what was going on with expect_deprecation_with_call_site(__FILE__, __LINE__ + 1)
. Let me know how I can update the spec to verify that the custom message is being shown.