Simplify wording in guide for unbraced closures

Author: joshtriplett

guide/expressions.md

@@ -123,8 +123,8 @@ elide types where possible.
 
 Use closures without the enclosing `{}`, if possible. Add the `{}` when you have
 a return type, when there are statements, when there are comments inside the
-closure, or when the body expression spans multiple lines and is a control-flow
-expression. If using braces, follow the rules above for blocks. Examples:
+closure, or when the body expression is a control-flow expression that spans
+multiple lines. If using braces, follow the rules above for blocks. Examples:
 
 ```rust
 |arg1, arg2| expr