bump gotest and emitter version

[tadelesh]

• The purpose of this PR is explained in this or a referenced issue.
• The PR does not update generated files.
  • These files are managed by the codegen framework at Azure/autorest.go.
• Tests are included and/or updated for code changes.
• Updates to module CHANGELOG.md are included.
• MIT license headers are included in each file.

[Copilot]

Pull request overview

This PR updates code generation and testing tool versions used in the Azure SDK for Go infrastructure. These are dependency version bumps for build and test tooling, not SDK module code changes.

• Updates @autorest/gotest from version 4.7.5 to 4.7.6
• Updates @azure-tools/typespec-go from version 0.8.5 to 0.8.6

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated no comments.

File	Description
eng/scripts/MgmtTestLib.ps1	Updates the default test extension version parameter for management SDK test generation
eng/emitter-package.json	Updates the TypeSpec Go emitter dependency version
eng/emitter-package-lock.json	Updates the lockfile with the new version, resolved URL, and integrity hash for the TypeSpec Go package

Files not reviewed (1)

• eng/emitter-package-lock.json: Language not supported