Remove warning when PATCH is idempotent

[kstich]

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

https://datatracker.ietf.org/doc/html/rfc5789#section-2

PATCH is neither safe nor idempotent as defined by [RFC2616], Section
9.1.

A PATCH request can be issued in such a way as to be idempotent,
which also helps prevent bad outcomes from collisions between two
PATCH requests on the same resource in a similar time frame.
Collisions from multiple PATCH requests may be more dangerous than
PUT collisions because some patch formats need to operate from a
known base-point or else they will corrupt the resource. Clients
using this kind of patch application SHOULD use a conditional request
such that the request will fail if the resource has been updated
since the client last accessed the resource. For example, the client
can use a strong ETag [RFC2616] in an If-Match header on the PATCH
request.