enable `/jira backport <git-branch-name>` to work.

Add branch name and jira target version to ocp/release configuration to enable /jira backport <git-branch-name> to work.
https://docs.ci.openshift.org/docs/architecture/jira/#configuration

Another option for backporting is the /jira backport command. This is similar to the above command but will instead create all of the backport issues immediately and then queue the cherrypick bot to create all specified cherrypick branches after the PR is merged, instead of one by one. This can be useful for repositories with very long running tests, as the tests for all backports will start immediately once the original PR is merged. These individual PRs must still be merged in the correct order. To be able to merge PRs for older releases after the release above it has merged, you will need to run /jira refresh on the PR to have the PR be marked as containing a valid issue. The format for the backport command is slightly different than the /cherrypick command, as instead of using spaces, the branches must be comma separated. And example of a valid command is /jira backport release-4.15,release-4.14,release-4.13.

Start with the ocp/release configuration and the Jira backport configuration documentation linked in the issue. Identify where branch names and Jira target versions are defined; done means the listed /jira backport release-4.15,release-4.14,release-4.13 form can use those entries.