Remove true/false defines in convert_UTF.cc

These are left over from when this file was written in C.

In C++, true and false are keywords, so this is no longer necessary.
In fact, redefining a keyword is not actually permitted in ISO C++
(https://eel.is/c++draft/macro.names#2), and is rejected by MSVC.

Change-Id: I2f4a6eae7f8dd4d91b8ee6588c7ae5e8f20bd0d0
Reviewed-on: https://chromium-review.googlesource.com/c/breakpad/breakpad/+/2105831
Reviewed-by: Mike Frysinger <vapier@chromium.org>
diff --git a/src/common/convert_UTF.cc b/src/common/convert_UTF.cc
index fe0e155..4a5df1e 100644
--- a/src/common/convert_UTF.cc
+++ b/src/common/convert_UTF.cc
@@ -78,13 +78,6 @@
 #define UNI_SUR_LOW_START   (UTF32)0xDC00
 #define UNI_SUR_LOW_END     (UTF32)0xDFFF
 
-#ifndef false
-#define false	   0
-#endif
-#ifndef true
-#define true	    1
-#endif
-
 /* --------------------------------------------------------------------- */
 
 ConversionResult ConvertUTF32toUTF16 (const UTF32** sourceStart, const UTF32* sourceEnd,