Fix adaptivity calling for explicit coupling

[IshaanDesai]

Adaptivity can be computed either once in a time window, or once in every time iteration. For explicit coupling scenarios, these two cases are one and the same. The current logic did not reflect this and hence adaptivity was incorrectly computed for explicit coupling scenarios. This PR fixes the problem.

Checklist:

• I added a summary of the changes (compared to the last release) in the CHANGELOG.md.
• I will remember to squash-and-merge, providing a useful summary of the changes of this PR.