deps(server): Update to Mongoose 8

[nellh]

This is a prerequisite for user migrations related to consolidating ORCID and Google accounts.

[codecov]

Codecov Report

Attention: Patch coverage is 37.50000% with 5 lines in your changes missing coverage. Please review.

Project coverage is 47.02%. Comparing base (eb6c606) to head (e33c9fa).
Report is 10 commits behind head on master.

Files with missing lines	Patch %	Lines
...openneuro-server/src/graphql/resolvers/metadata.ts	25.00%	3 Missing ⚠️
...nneuro-server/src/graphql/resolvers/permissions.ts	0.00%	1 Missing ⚠️
...ges/openneuro-server/src/graphql/resolvers/user.ts	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3302   +/-   ##
=======================================
  Coverage   47.02%   47.02%           
=======================================
  Files         583      583           
  Lines       36945    36946    +1     
  Branches     1174     1174           
=======================================
+ Hits        17372    17374    +2     
+ Misses      19386    19385    -1     
  Partials      187      187           

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