t/t0006: specify timezone as EST5 not EST to comply with POSIX

POSIX requires that both the timezone "standard" and "offset" be specified
in the TZ environment variable.  This causes a problem on IRIX which does
not understand the timezone 'EST'.
Signed-off-by: NBrandon Casey <casey@nrlssc.navy.mil>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

t/t0006-date.sh

@@ -39,7 +39,7 @@ check_parse 2008-02 bad
 check_parse 2008-02-14 bad
 check_parse '2008-02-14 20:30:45' '2008-02-14 20:30:45 +0000'
 check_parse '2008-02-14 20:30:45 -0500' '2008-02-14 20:30:45 -0500'
-check_parse '2008-02-14 20:30:45' '2008-02-14 20:30:45 -0500' EST
+check_parse '2008-02-14 20:30:45' '2008-02-14 20:30:45 -0500' EST5
 
 check_approxidate() {
 	echo "$1 -> $2 +0000" >expect