Remove FS_Read2().

Functionally the same as FS_Read().
Streaming functionality was removed in https://github.com/ioquake/ioq3/commit/672cfbf16f83fb67f6ce9bb1d3571dc32a5b3083 but flag remained.

code/qcommon/qcommon.h

@@ -659,7 +659,6 @@ int		FS_FileIsInPAK(const char *filename, int *pChecksum );
 
 int		FS_Write( const void *buffer, int len, fileHandle_t f );
 
-int		FS_Read2( void *buffer, int len, fileHandle_t f );
 int		FS_Read( void *buffer, int len, fileHandle_t f );
 // properly handles partial reads and reads from other dlls