Remove obsolete StaticPage test.

The test cand be found here: https://github.com/ezsystems/StudioUIBundle/tree/master/Tests/FieldType

Originally is was added here: https://github.com/ezsystems/StudioUIBundle/commit/a7beb5c47f2f28fc2083590fa7f7139530eb19bc

Then here code was removed but test left behind: https://github.com/ezsystems/StudioUIBundle/commit/9e6a4614a0f7776f9f92c93e7551a75eaa916113#diff-f4aff4235a9f33c4c2be4035e530ee05