[stdlib] Minor comment fix. Re: Cleaned up test_comparison_operators(…

…) in test_string_literal.mojo and test_string.mojo in an attempt to make the tests more readable.

Signed-off-by: Simon Hellsten <simonhellsten@hotmail.com>

stdlib/test/builtin/test_string_literal.mojo

@@ -95,7 +95,7 @@ fn test_comparison_operators() raises:
     assert_false("ab" >= "abc")
     assert_true("abcd" >= "abc")
 
-    # Test case sensitivity in comparison
+    # Test case sensitivity in comparison (assuming ASCII order)
     assert_true("abc" > "ABC")
     assert_false("abc" <= "ABC")