[Hackday][2.7] Added deprecated notes to '_method' and '_scheme' route requirements

| Q             | A
| ------------- | ---
| Bug fix?      | [no]
| New feature?  | [no]
| BC breaks?    | [no]
| Deprecations? | [yes]
| Tests pass?   | [no]
| Fixed tickets | [#12641, #12640]
| License       | MIT
| Doc PR        |