Updating release instructions to run the upmerge workflows from edge

[willdavsmith]

Description

• Update release instructions to run the upmerge workflows from edge

Type of change

• This pull request fixes a bug in Radius and has an approved issue (issue link required).
• This pull request adds or changes features of Radius and has an approved issue (issue link required).
• This pull request is a minor refactor, code cleanup, test improvement, or other maintenance task and doesn't change the functionality of Radius (issue link optional).

Fixes: #issue_number

Contributor checklist

Please verify that the PR meets the following requirements, where applicable:

• An overview of proposed schema changes is included in a linked GitHub issue.
• A design document PR is created in the design-notes repository, if new APIs are being introduced.
• If applicable, design document has been reviewed and approved by Radius maintainers/approvers.
• A PR for the samples repository is created, if existing samples are affected by the changes in this PR.
• A PR for the documentation repository is created, if the changes in this PR affect the documentation or any user facing updates are made.
• A PR for the recipes repository is created, if existing recipes are affected by the changes in this PR.

[sk593]

Do we need to update the upmerge workflows as well? Right now, the workflows merge changes from the input branch (the release branch) into an upmerge branch created from edge: https://github.com/radius-project/docs/blob/c2bdd09fd98f889fbbc095e930bb7dea4fe717cb/.github/workflows/upmerge.yaml#L66.

We might need to track the release version as an input to make sure the workflow runs as expected. We should open issues in the samples/docs repos to track updating the workflows and merge this PR for the release docs after