Slightly clarify why guards

lib/elixir/pages/references/patterns-and-guards.md

@@ -270,7 +270,7 @@ Suffix matches (`hello <> " world"`) are not valid patterns.
 
 Guards are a way to augment pattern matching with more complex checks. They are allowed in a predefined set of constructs where pattern matching is allowed, such as function definitions, case clauses, and others.
 
-Not all expressions are allowed in guard clauses, but only a handful of them. This is a deliberate choice. This way, Elixir (and Erlang) can make sure that nothing bad happens while executing guards and no mutations happen anywhere. It also allows the compiler to optimize the code related to guards efficiently.
+Not all expressions are allowed in guard clauses, but only a handful of them. This is a deliberate choice. This way, Elixir (through Erlang) ensures that all guards are predictable (no mutations or other side-effects) and they can be optimized and performed efficiently.
 
 ### List of allowed functions and operators