chore: remove v prefix from release tags

[marandaneto]

💡 Motivation and Context

This ports the same release-workflow fix from posthog-go to posthog-elixir. The workflow currently creates GitHub releases with a v prefix, but this repo should publish plain semantic version tags/releases like 1.2.3.

💚 How did you test it?

• ruby -e 'require "yaml"; YAML.load_file(".github/workflows/release.yml"); puts "yaml-ok"'
• git diff --check

📝 Checklist

• I reviewed the submitted code.
• I added tests to verify the changes.
• I updated the docs if needed.
• No breaking change or entry added to the changelog.

If releasing new changes

• Ran sampo add to generate a changeset file
• Added the release label to the PR

[github-actions]

posthog-elixir Compliance Report

Date: 2026-04-20 07:15:15 UTC
Duration: 191ms

⚠️ Some Tests Failed

0/1 tests passed, 1 failed

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Feature_Flags Tests

⚠️ 0/1 tests passed, 1 failed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	❌	6ms

Failures

request_payload.request_with_person_properties_device_id

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'