Use mock in SpecialPageCopyrightViewTest

this fixes failure on travis, where the test
indirectly depended on content language setting.

We can use a mock and then not be concerned about
content language at all.

Change-Id: I60c0b201807b05d2b4e5847bfe4ccaed204cb86b
Merge "Use mock in SpecialPageCopyrightViewTest"