Re-add call to mark_activity_occurred

Commit 2a537ce8a1ad4d0bf0b8e841478dfc0980927aae
added an mark_activity_occurred call from update.

The very next commit for this file
0fecc6c310b06ba188f4055a1a4458baf2887f67
removed this call.

This commit re-adds it. We need this call after update
because users can get stuck when performing activities
for an event at the informed consent activity for a participant
with an existing consent.

Changes in #3170 and specifically the task #3194 should
address the issue.
Merge branch 'master' of https://github.com/NUBIC/ncs_navigator_core
Updated specs to use custom_recruitment_strategy

Both these specs used a method 'set_recruitment_strategy'
which set the NcsNavigatorCore.recruitment_strategy.
While fine when running the specs individually this caused
several errors in the CI build.

When updating application level configuration variables in tests
we should take care to revert that value back to the original value
after the test needing the change has run.