Add test coverage for residual_fringe step

[stscijgbot-jp]

Issue JP-3900 was created on JIRA by Melanie Clarke:

Since the residual fringe step is off by default, it is not covered by standard MIRI MRS spec2 regression tests.  We should add a test that turns the step on, to make sure we catch regressions.

Unit test coverage for this module is also currently very minimal.  We should add some tests to make sure this step continues to work.

Since this step is not currently covered at all, it looks like it was overlooked in testing for numpy 2 compatibility.  It requires BayesicFitting>=3.2.2 to run with numpy>2; the current minimum pin in jwst is 3.0.1.

[stscijgbot-jp]

Comment by David Law on JIRA:

Good catch!