doc: keep prev style

needed to use the github editor to have fast preview. I don't know how else to get the "Submitting Patches" look for the ol/li elements.

CONTRIBUTING.md

@@ -15,21 +15,21 @@ Please be aware of at least these common problems:
 
 1. Async and Cancellation
 
-  Any future can be cancelled at every await point unless it's a top
-level spawned future. Most common reasons to be cancelled or
-dropped is that a future is polled or raced within `tokio::select!`
-with a cancellation token or the HTTP client drops the connection,
-causing a cancellation or drop on a handler future.
+    Any future can be cancelled at every await point unless it's a top
+    level spawned future. Most common reasons to be cancelled or
+    dropped is that a future is polled or raced within `tokio::select!`
+    with a cancellation token or the HTTP client drops the connection,
+    causing a cancellation or drop on a handler future.
 
 2. When using `scopeguard` or generally within `Drop::drop`, the code
-must not panic.
+must not panic
 
-  `scopeguard` can be handy for simple operations, such as
-decrementing a metric, but it can easily obscure that the code will
-run on `Drop::drop`. Should a panic happen and the implemented drop
-also panic when unwinding, the rust runtime will abort the process.
-Within a multi-tenant system, we don't want to abort, at least for
-accidental `unwrap` within a `Drop::drop`.
+    `scopeguard` can be handy for simple operations, such as
+    decrementing a metric, but it can easily obscure that the code will
+    run on `Drop::drop`. Should a panic happen and the implemented drop
+    also panic when unwinding, the rust runtime will abort the process.
+    Within a multi-tenant system, we don't want to abort, at least for
+    accidental `unwrap` within a `Drop::drop`.
 
 ## Submitting changes