truncated paragraph on planner rules in tutorial.html

[Alexey Roytman]

In the "Optimizing queries using planner rules" section of this 
document: https://calcite.apache.org/docs/tutorial.html
we have a paragraph, looking like this:
--- start
This negotiation is a simple form of query optimization. Calcite 
supports query optimization by adding /planner rules/. Planner rules 
operate by looking for patterns in the query parse tree (for instance a 
project on top of a certain kind of table), and
---end
It is truncated.

- Alexey.