test: remove stale net6.0/net7.0 verified snapshots

[jamescrosswell]

Summary

Deletes six dead Verify snapshots for net6.0/net7.0:

test/Sentry.Tests/SentryOptionsTests.Integrations_default_ones_are_properly_registered.DotNet6_0.DotNet.verified.txt
test/Sentry.Tests/SentryOptionsTests.Integrations_default_ones_are_properly_registered.DotNet6_0.OSX.DotNet.verified.txt
test/Sentry.Tests/SentryOptionsTests.Integrations_default_ones_are_properly_registered.DotNet6_0.Windows.DotNet.verified.txt
test/Sentry.Tests/SentryOptionsTests.Integrations_default_ones_are_properly_registered.DotNet7_0.DotNet.verified.txt
test/Sentry.Tests/SentryOptionsTests.Integrations_default_ones_are_properly_registered.DotNet7_0.OSX.DotNet.verified.txt
test/Sentry.Tests/SentryOptionsTests.Integrations_default_ones_are_properly_registered.DotNet7_0.Windows.DotNet.verified.txt

The test uses .UniqueForTargetFrameworkAndVersion(), so Verify only ever resolves a snapshot whose suffix matches a TFM currently being built. net6.0/net7.0 were dropped in #3807, which left these behind; nothing has been able to select them since.

Closes #5530

#skip-changelog

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.66%. Comparing base (b96ff3b) to head (8d2ed9e).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5531      +/-   ##
==========================================
- Coverage   74.67%   74.66%   -0.02%     
==========================================
  Files         515      515              
  Lines       18909    18909              
  Branches     3691     3691              
==========================================
- Hits        14120    14118       -2     
- Misses       3904     3906       +2     
  Partials      885      885              

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