Update RuleDocumentation.md

Author: alexandersandberg

Documentation/RuleDocumentation.md

@@ -243,7 +243,7 @@ Format: The access level is removed from the extension declaration and is added
 Assignment expressions must be their own statements.
 
 Assignment should not be used in an expression context that expects a `Void` value. For example,
-assigning a variable within a `return` statement existing a `Void` function is prohibited.
+assigning a variable within a `return` statement exiting a `Void` function is prohibited.
 
 Lint: If an assignment expression is found in a position other than a standalone statement, a
       lint finding is emitted.