Update Go publishing documentation with automatic publishing info

[devin-ai-integration]

Summary

Updates the Go publishing documentation to clarify that Go SDKs are automatically published to pkg.go.dev when repository requirements are met. This addresses customer confusion about Go SDK publishing (per internal Slack thread about Merge's Go SDK).

Key changes:

• Clarifies that no dedicated CI is needed for publishing - it's automatic
• Adds two new requirements: valid Go module path in go.mod and semantic version tag
• Adds the exact URL where SDK is published: https://pkg.go.dev/<go-module-path-in-go.mod>
• Adds a Warning about module path versioning - if go.mod has a /v2 suffix, the SDK publishes to a different URL
• Updates step title from "Publish on pkg.go.dev" to "Verify on pkg.go.dev" to reflect automatic nature
• Updates URL placeholders to use <go-module-path-in-go.mod> for consistency

Review & Testing Checklist for Human

• Verify the Warning about /v2 module path versioning is technically accurate and clearly explains the issue
• Check that the URL format https://pkg.go.dev/<go-module-path-in-go.mod> is correct and matches Go's actual behavior
• Preview the page to ensure the Warning component renders properly

Notes

Link to Devin run: https://app.devin.ai/sessions/1aee80761ff84568813b7a31fd67562e
Requested by: Fern Support (info@buildwithfern.com)

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🌿 Preview your docs: https://fern-preview-a8ca11c5-de90-486a-bacb-3d60967fb113.docs.buildwithfern.com/learn

Visual changes detected:

fern/products/sdks/overview/go/publishing-to-go-package-manager.mdx

Page: learn/sdks/generators/go/publishing | Change: 75.40482699892435%