Reschedule finishing block to the first() phase of the final tick

[bodkan]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 81.25000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 90.23%. Comparing base (29404e7) to head (130735a).
Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
R/msprime.R	81.81%	2 Missing ⚠️
R/slim.R	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #160      +/-   ##
==========================================
- Coverage   90.27%   90.23%   -0.05%     
==========================================
  Files          11       11              
  Lines        3207     3214       +7     
==========================================
+ Hits         2895     2900       +5     
- Misses        312      314       +2     

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