autotests: Drop effect loader tests

Effect loading is already tested using integration tests, for example
the maximize test verifies that the maximize effect is loaded _and_ it
actually does something useful when a window is maximized or restored,
testScriptedEffectLoader only verifies that the effect is loaded, which
is less helpful than what integration tests provide us.

But perhaps the main problem with these tests is that they require us
building a mockverse around them. This litters code with ifdef
preprocessor directives and makes changing such code a living nightmare.

Another problem with these two tests is that they cannot use OpenGL
because it means mocking OpenGL, which we obviously not going to do.
With integration tests, it's not a problem.

The bottom line is that unit tests can be useful but they make life
notoriously difficult when it comes to testing components that depend on
other components.