lc: remove date delta check from lc header checks

This was prone to false positives.  We still check:
1. the expiration header has valid form
2. the rule-id matches

Signed-off-by: Matt Benjamin <mbenjamin@redhat.com>

s3tests_boto3/functional/test_s3.py

@@ -8937,7 +8937,6 @@ def check_lifecycle_expiration_header(response, start_time, rule_id,
 
     expiration = datetime.datetime.strptime(m.group(1),
                                             '%a, %d %b %Y %H:%M:%S %Z')
-    eq((expiration - start_time).days, delta_days)
     eq(m.group(2), rule_id)
 
     return True