Bump version from 0.9.7.post1 to 0.9.8.dev

[rflamary]

Types of changes

Motivation and context / Related issue

How has this been tested (if it applies)

PR checklist

• I have read the CONTRIBUTING document.
• The documentation is up-to-date with the changes I made (check build artifacts).
• All tests passed, and additional code has been covered with new tests.
• I have added the PR and Issue fix to the RELEASES.md file.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.86%. Comparing base (9932112) to head (755b158).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #841   +/-   ##
=======================================
  Coverage   96.85%   96.86%           
=======================================
  Files         128      128           
  Lines       25683    25683           
=======================================
+ Hits        24876    24878    +2     
+ Misses        807      805    -2     

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