Update conf.py - Githubissues

replace version number with 'develop'

Pull Request Testing

[ ] Describe testing already performed for these changes:
[ ] Recommend testing for the reviewer(s) to perform, including the location of input datasets, and any additional instructions:
[ ] Do these changes include sufficient documentation updates, ensuring that no errors or warnings exist in the build of the documentation? [Yes or No]
[ ] Do these changes include sufficient testing updates? [Yes or No]
[ ] Will this PR result in changes to the test suite? [Yes or No]
If yes, describe the new output and/or changes to the existing output:
[ ] Please complete this pull request review by [Fill in date].

See the METplus Workflow for details.

[ ] Add any new Python packages to the METplus Components Python Requirements table.
[ ] Review the source issue metadata (required labels, projects, and milestone).
[ ] Complete the PR definition above.
[ ] Ensure the PR title matches the feature or bugfix branch name.
[ ] Define the PR metadata, as permissions allow. Select: Reviewer(s) Select: Organization level software support Project or Repository level development cycle Project Select: Milestone as the version that will include these changes
[ ] After submitting the PR, select the :gear: icon in the Development section of the right hand sidebar. Search for the issue that this PR will close and select it, if it is not already selected.
[ ] After the PR is approved, merge your changes. If permissions do not allow this, request that the reviewer do the merge.
[ ] Close the linked issue and delete your feature or bugfix branch from GitHub.