Fix template placeholder dates

[gaiksaya]

Description

The dates mentioned on https://opensearch.org/releases/ do not match the release template dates.
Fixing it in this PR.

Issues Resolved

List any issues this PR will resolve, e.g. Closes [...].

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[github-actions]

PR Reviewer Guide 🔍

Here are some key observations to aid the review process:

🧪 No relevant tests

🔒 No security concerns identified

✅ No TODO sections

🔀 No multiple PR themes

⚡ Recommended focus areas for review Inconsistent Dates The "Code Complete" and "Release Branch, Release Candidate Creation and Testing" sections both end on __REPLACE_RELEASE-minus-14-days__. It should be verified whether these two phases are intentionally set to the same end date, or if one of them has an incorrect value. ### [Code Complete](https://github.com/opensearch-project/opensearch-build/wiki/Releasing-the-Distribution#code-complete-and-feature-freeze) - _Ends __REPLACE_RELEASE-minus-14-days___ - [ ] Mark this as done once the [Code Complete](https://github.com/opensearch-project/opensearch-build/wiki/Releasing-the-Distribution#code-complete-and-feature-freeze) is reviewed. - [ ] Create/Verify pull requests to add each component to relase input [manifests/{{ env.VERSION }}/opensearch-{{ env.VERSION }}.yml](/opensearch-project/opensearch-build/tree/main/manifests/{{ env.VERSION }}/opensearch-{{ env.VERSION }}.yml) and [manifests/{{ env.VERSION }}/opensearch-dashboards-{{ env.VERSION }}.yml](/opensearch-project/opensearch-build/tree/main/manifests/{{ env.VERSION }}/opensearch-dashboards-{{ env.VERSION }}.yml). ### [Release Branch, Release Candidate Creation and Testing](https://github.com/opensearch-project/opensearch-build/wiki/Releasing-the-Distribution#release-candidate-creation-and-testing) - _Ends __REPLACE_RELEASE-minus-14-days___

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.62%. Comparing base (7d81538) to head (312a8e1).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6178   +/-   ##
=======================================
  Coverage   96.62%   96.62%           
=======================================
  Files         405      405           
  Lines       19039    19039           
=======================================
  Hits        18397    18397           
  Misses        642      642           

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