Revert "headers: Use _FILE_OFFSET_BITS == 64 also for 64-bit truncate definition"

This reverts commit fe79aeb.

This change broke building user apps with Qt, if the unistd.h
header has been included before. Qt classes have methods named
"truncate", and they have a guard like this at the top of a
number of headers (e.g. qstring):

    #ifdef truncate
    #error qstring.h must be included before any header file that defines truncate
    #endif

https://github.com/qt/qtbase/blob/v6.10.0/src/corelib/text/qstring.h#L35

Signed-off-by: Martin Storsjö <[email protected]>

Author: mstorsjo

mingw-w64-headers/crt/unistd.h

@@ -66,7 +66,6 @@ int truncate64(const char *, _off64_t);
 #define _FILE_OFFSET_BITS_SET_FTRUNCATE
 #if (defined(_FILE_OFFSET_BITS) && (_FILE_OFFSET_BITS == 64))
 #define ftruncate ftruncate64
-#define truncate truncate64
 #endif /* _FILE_OFFSET_BITS_SET_FTRUNCATE */
 #endif /* _FILE_OFFSET_BITS_SET_FTRUNCATE */