Bump prio-graph version to 0.2.1

[apfitzge]

Problem

• prio-graph 0.2.0 had a bug which did not correctly track write-read conflicts if there were multiple reads after a write. This is fixed in 0.2.1 - see Bugfix: Reads track most recent write apfitzge/prio-graph#57
• If the write had higher-priority, the scheduler will still have scheduled the write first. However, if they had the same priority, it could have led to an inconsistent scheduling order.

Summary of Changes

• Bump prio-graph version

Fixes #

---

Close #34606

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (5349308) 81.8% compared to head (4b53204) 81.8%.
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##           master   #34604     +/-   ##
=========================================
- Coverage    81.8%    81.8%   -0.1%     
=========================================
  Files         824      824             
  Lines      222260   222260             
=========================================
- Hits       181910   181897     -13     
- Misses      40350    40363     +13