Migrate Proposal from Google Doc: Making durations and number literals the same

| Document | Initial date | Status | Pull requests |
| -------- | ------------ | ------ | ------------- |
| [Making durations and number literals the same](https://docs.google.com/document/d/1LaZfknXuuRWGtQSbULoMtclQhuLUMrdwg15wMvoBvCQ/edit) | 2021‑07‑26 | In progress | [#9138](https://github.com/prometheus/prometheus/pull/9138) |