Apply suggestions from code review

Co-authored-by: Greg Lueck <[email protected]>

Author: sergei

sycl/doc/PreprocessorMacros.md

@@ -43,14 +43,14 @@ This file describes macros that have effect on SYCL compiler and run-time.
   Defining as non-zero enables the fallback assert feature even on devices
   without native support. Be aware that this will add some overhead that is
   associated with submitting kernels that call `assert()`. When this macro is
-  not defined, the logic for detecting assertion failures in kernels is
+  defined as 0 or is not defined, the logic for detecting assertion failures in kernels is
   disabled, so a failed assert will not cause a message to be printed and will
   not cause the program to abort. Some devices have native support for
   assertions. The logic for detecting assertion failures is always enabled on
   these devices regardless of whether this macro is defined because that logic
   does not add any extra overhead. One can check to see if a device has native
   support for `assert()` via `aspect::ext_oneapi_native_assert`.
-  Default value is 0.
+  This macro is undefined by default.
 
 ## Version macros