doc: edit reason-for-deprecation text

It's not clear (to me, at least) how describing an API as  "considered
to be unsafe" differs from describing it as simply "unsafe". Use the
shorter, latter wording.

PR-URL: #28098
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>

doc/api/deprecations.md

@@ -5,7 +5,7 @@
 
 Node.js may deprecate APIs for any of the following reasons:
 
-* Use of the API is considered to be unsafe.
+* Use of the API is unsafe.
 * An improved alternative API is available.
 * Breaking changes to the API are expected in a future major release.