Syntax for variable interpolation in custom dashboards

Summary

Which syntax should we continue to support for variable interpolation in custom dashboards?

%{}

This is the Ruby syntax that we've supported for a long time.

{{}}

This is the Liquid syntax that was introduced in 12.7. This syntax is also used in series labels.

Both the above

We currently support both the above syntaxes.

Proposal

Switch to supporting only the {{}} syntax. It makes it consistent with the syntax we use for series labels. This is the plan we announced back in 12.6.