tests(instance): bump go-vcr to v4 for instance package

[Mia-Cross]

This PR starts the migration of tests cassettes from go-vcr.v3 to go-vcr.v4 with the instance package.
Both versions of go-vcr can coexist in the same go.mod so we decided to migrate one package at a time.

This migration will allow us to have smaller cassettes thanks to the omitempty tag that was added to the Request and Response structs in v4, so empty fields like transfer_encoding and trailer will not appear in the cassettes.

• Find out why the empty fields came back in this PR

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 47 lines in your changes missing coverage. Please review.
✅ Project coverage is 1.66%. Comparing base (f89b981) to head (bf1391f).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
internal/acctest/acctest.go	0.00%	47 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##           master   #3426      +/-   ##
=========================================
- Coverage    1.67%   1.66%   -0.01%     
=========================================
  Files         391     391              
  Lines       43216   43262      +46     
=========================================
- Hits          722     720       -2     
- Misses      42412   42459      +47     
- Partials       82      83       +1     

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