Revert "Alias TRUE and FALSE to C99's true and false"

This reverts commit 67d89a5a87.

Turns out that C++ doesn't like it when stuff goes from an integer to a
boolean.

See: https://gitlab.gnome.org/GNOME/gnome-build-meta/-/merge_requests/2900

glib/gmacros.h

@@ -39,9 +39,6 @@
  */
 #include <stddef.h>
 
-/* We include stdbool.h to get the system's definition of true and false */
-#include <stdbool.h>
-
 /*
  * Note: Clang (but not clang-cl) defines __GNUC__ and __GNUC_MINOR__.
  * Both Clang 11.1 on current Arch Linux and Apple's Clang 12.0 define
@@ -925,11 +922,11 @@
 #endif
 
 #ifndef	FALSE
-#define	FALSE	false
+#define	FALSE	(0)
 #endif
 
 #ifndef	TRUE
-#define	TRUE	true
+#define	TRUE	(!FALSE)
 #endif
 
 #undef	MAX