Merge `new project` templates into one (#24985)
Additionally simplify the `new project` template slightly.
Review hint: Disable whitespace changes.
<details><summary>Before</summary>
## New repo project
## Edit repo project
## New user/org project
## Edit user/org project
</details>
<details><summary>After</summary>
## New repo project
## Edit repo project
## New user/org project
## Edit user/org project
</details>
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Co-authored-by: Giteabot <teabot@gitea.io>
