Fix Gremlin Server 3.7

[kmcginnes]

Graph Explorer breaks in Gremlin Server 3.7 because the response content type changed from 3.6.

To ensure we always get the content type we expect we set the header:

"Accept": "application/vnd.gremlin-v3.0+json"

This is done on the client and the server.

Validation

• Test with Gremlin Server 3.6
• Test with Gremlin Server 3.7
• Test with Neptune 1.3

Related Issues

• Fixes [Bug] Support for Gremlin Server 3.7 is broken #277

Check List

• I confirm that my contribution is made under the terms of the Apache 2.0
  license.
• I have run pnpm checks to ensure code compiles and meets standards.
• I have run pnpm test to check if all tests are passing.
• I have covered new added functionality with unit tests if necessary.
• I have added an entry in the Changelog.md.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 7 lines in your changes are missing coverage. Please review.

Project coverage is 14.94%. Comparing base (361c4ba) to head (8ae0601).
Report is 20 commits behind head on main.

Files	Patch %	Lines
...-explorer/src/connector/gremlin/gremlinExplorer.ts	0.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #411      +/-   ##
==========================================
+ Coverage   13.97%   14.94%   +0.96%     
==========================================
  Files         414      415       +1     
  Lines       30639    30809     +170     
  Branches      878      953      +75     
==========================================
+ Hits         4283     4604     +321     
+ Misses      26026    25878     -148     
+ Partials      330      327       -3     

Flag	Coverage Δ
unittests	14.94% <0.00%> (+0.96%)	⬆️

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