test: Update Flask dependency

[Stranger6667]

No description provided.

[codecov-commenter]

Codecov Report

Merging #1458 (5f25e97) into master (52842e0) will increase coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1458      +/-   ##
==========================================
+ Coverage   99.10%   99.13%   +0.02%     
==========================================
  Files          86       86              
  Lines        6672     6672              
  Branches     1168     1168              
==========================================
+ Hits         6612     6614       +2     
+ Misses         31       30       -1     
+ Partials       29       28       -1     

Impacted Files	Coverage Δ
src/schemathesis/extra/pytest_plugin.py	100.00% <0.00%> (+1.75%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 52842e0...5f25e97. Read the comment docs.