sh-i18n--envsubst.c: do not #include getopt.h

The getopt.h header file is not used.  It's inclusion is left over from the
original version of this source.  Additionally, getopt.h does not exist on
all platforms (SunOS 5.7) and will cause a compilation failure.  So, let's
remove it.
Signed-off-by: NBrandon Casey <casey@nrlssc.navy.mil>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

sh-i18n--envsubst.c

@@ -51,7 +51,6 @@
    Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
 
 #include <errno.h>
-#include <getopt.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>