Fix broken test on 32-bit PHP systems.

This triggers a bug in data model on 32-bit PHP systems. I added
a test for this issue:
https://github.com/wmde/WikibaseDataModel/pull/135

This test here is unrelated and can be simplified now that there
is an other test for the same issue.

Change-Id: Ie2c3121a644480bb9d2b09ff197e6a9703ddcc2b
Merge "Fix broken test on 32-bit PHP systems."