docs: Remove remaining API V1 documentation (DEV-3073)

[BalduinLandolt]

Pull Request Checklist

Task Description/Number

Issue Number: DEV-

PR Type

• build/chore: maintenance tasks (no production code change)
• docs: documentation changes (no production code change)
• feat: represents new features
• fix: represents bug fixes
• perf: performance improvements
• refactor: represents production code refactoring
• test: adding or refactoring tests (no production code change)

Basic requirements for bug fixes and features

• Tests for the changes have been added
• Docs have been added / updated

Does this PR introduce a breaking change?

• Yes

Does this PR change client-test-data?

• Yes

[linear]

DEV-3073 DSP-API: remove v1 docs

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (95ad2f9) 11.62% compared to head (0347357) 88.56%.
Report is 3 commits behind head on main.

Files	Patch %	Lines
...s/v2/responder/valuemessages/ValueMessagesV2.scala	98.24%	1 Missing ⚠️
...i/slice/admin/domain/service/DspIngestClient.scala	93.75%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2970       +/-   ##
===========================================
+ Coverage   11.62%   88.56%   +76.94%     
===========================================
  Files         246      246               
  Lines       22870    22907       +37     
===========================================
+ Hits         2658    20288    +17630     
+ Misses      20212     2619    -17593     

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