clarify comment

Author: Marc Rasi

test/SILOptimizer/pound_assert.swift

@@ -103,10 +103,9 @@ func test_trapsAndOverflows() {
   // expected-error @+1 {{arithmetic operation '124 + 92' (on type 'Int8') results in an overflow}}
   #assert((124 as Int8) + 92 < 42)
 
-  // The error message below is generated by the traditional constant folder.
-  // The constant folder responsible for #assert does generate an error message
-  // because the traditional constant folder does not replace the condition
-  // with a constant.
+  // One error message below is generated by the traditional constant folder.
+  // The constant folder responsible for #assert does generate an additional
+  // error message.
   // expected-error @+2 {{integer literal '123231' overflows when stored into 'Int8'}}
   // expected-error @+1 {{#assert condition not constant}}
   #assert(Int8(123231) > 42)