[Building Sakai] Fix to 2.8.0 -> 2.8.1 Oracle conversion script

[Seth Theriault]

Hello,

I have just committed a fix for a bug introduced into the Oracle 
2.8.0 -> 2.8.1 conversion script earlier in the cycle. 
Sepcifically, the alter statement for the KNL-563 correction:

-- KNL-563 correction
-- sakai-2.8.0 conversion script set DEFAULT_VALUE incorrectly to not null.  Set to null to match Hibernate mapping.
alter table SAKAI_MESSAGE_BUNDLE modify DEFAULT_VALUE text null;

is wrong. Instead, it should read:

alter table SAKAI_MESSAGE_BUNDLE modify DEFAULT_VALUE null;

This was identified in the testing:

https://jira.sakaiproject.org/browse/SAK-20935

but not committed until just now. The merge revisions are:

trunk, 99087
2.8.x branch, 99088
2.8.1 branch, 99089

Seth