stylistic changes per PR change req. in description

https://github.com/Semmle/ql/pull/1078#pullrequestreview-214401005

javascript/ql/src/semmle/javascript/Functions.qll

@@ -159,13 +159,12 @@ class Function extends @function, Parameterized, TypeParameterized, StmtContaine
   }
 
   /** 
-   * Gets a return from a function which has undefined value (i.e. implicit returns
-   * and returns w/o expressions).
-   */
-   
-  /* Functions can have undefined returns in a few different ways:
+   * Gets a return from a function which has undefined value (that is, implicit
+   * returns and returns without expressions).
+   *
+   * Functions can have undefined returns in a few different ways:
    * 
-   * 1. An explicit return statement with no expression, i.e. the statement `return;`
+   * 1. An explicit return statement with no expression (the statement `return;`)
    * 
    * 2. An implicit return resulting from an expression executing as the last thing
    *    in the function. For example, the test in a final `if` statement:

javascript/ql/test/library-tests/Functions/undefinedreturns.js

@@ -4,7 +4,7 @@
 
 //////////////////
 //              //
-//  GOOD CASES  //
+//  DON'T FIND  //
 //              //
 //////////////////
 
@@ -18,11 +18,11 @@ function fn_w_final_return_w_expr() { return 1; }
 
 
 
-/////////////////
-//             //
-//  BAD CASES  //
-//             //
-/////////////////
+////////////
+//        //
+//  FIND  //
+//        //
+////////////
 
 function fn_w_empty_body() { }
 function fn_w_final_return_wo_expr() { return; }