Expand reddit_ads version range to include v1.6.0

[julianarombo]

PR Overview

Package version introduced in this PR:

• v2.8.0 (joins the unreleased v2.8.0 alongside Bump tiktok_ads Smart+ ads join fix #187)

This PR addresses the following Issue/Feature(s):

• Upstream: Remove unused optimization_strategy_type and is_processing fields from ad_group and ad staging models dbt_reddit_ads#41

Summary of changes:

• Expands the supported reddit_ads package range from [">=1.5.0", "<1.6.0"] to [">=1.5.0", "<1.7.0"] so Ad Reporting picks up reddit_ads v1.6.0.
• reddit_ads v1.6.0 removes the deprecated optimization_strategy_type field from stg_reddit_ads__ad_group and is_processing from stg_reddit_ads__ad. Neither field is used in any ad_reporting models, so the impact is limited to users selecting them directly from the Reddit staging models.
• Updates the README dependency snippet and the install range to v2.8.0, and adds the Reddit changes to the existing v2.8.0 CHANGELOG entry.

Submission Checklist

• Alignment meeting with the reviewer (if needed)
  • Timeline and validation requirements discussed
• Provide validation details:
  • Validation Steps: Check for unintentional effects (e.g., add/run consistency & integrity tests)
  • Testing Instructions: Confirm the change addresses the issue(s)
  • Focus Areas: Complex logic or queries that need extra attention
• Merge any relevant open PRs into this PR (none)

Changelog

• Draft changelog for PR
• Final changelog for release review