[sync] Update to DashMap 6

[GnomedDev]

This is a breaking change due to the removal of the S generic parameter from EntryRef, but improves performance a ton apparently.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.84%. Comparing base (af40a12) to head (309fa89).
Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #34      +/-   ##
==========================================
- Coverage   91.90%   91.84%   -0.06%     
==========================================
  Files          23       23              
  Lines        4125     4097      -28     
==========================================
- Hits         3791     3763      -28     
  Misses        334      334              

[GnomedDev]

I could have bumped MSRV up to 1.65 for dashmap 6, but since 1.76 came out 6 months ago this can remove the version restriction on triomphe.

[tatsuya6502]

Thank you! It looks good to me.

Just FYI, before releasing next version of mini-moka with this DashMap update, I will try to remove triomphe from the dependency and copy necessary codes from triomphe to mini-moka. (a relevant comment in a moka's issue). And then I will change the MSRV to 1.65. I am hoping to do it in next weekend.

If it takes too long, I will release the next version of mini-moka without removing triomphe. And its MSRV will be 1.76.