doc: edit text about revoking deprecations

* "un-deprecation" ಠ_ಠ -> "revoking deprecations"
* "From time-to-time" -> "Occastionally"
* "semver-major" and "semver-minor" are jargon that readers who don't
  follow our issue tracker will not know. Remove the sentence as it
  doesn't really impact end users. The deprecation is revoked when it is
  revoked. Rules around the releases where deprecations can be revoked
  may be added to the COLLABORATOR_GUIDE in the extensive section about
  deprecations there. If so, great, but let's still remove it here as
  having the information scattered in two places makes it likely that
  one will be edited to contradict the other and then it won't be clear
  which one is correct.
* Remove unneeded italics. The italicized sentence is not hugely
  critical information that we desperately want users to know. Most
  users won't care. They will only care about the deprecation message
  that they are looking up at that moment.

PR-URL: #20519
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

doc/api/deprecations.md

@@ -30,12 +30,11 @@ cause an error to be thrown.
 An End-of-Life deprecation is used to identify code that either has been
 removed or will soon be removed from Node.js.
 
-## Un-deprecation
+## Revoking deprecations
 
-From time-to-time the deprecation of an API may be reversed. Such action may
-happen in either a semver-minor or semver-major release. In such situations,
+Occasionally, the deprecation of an API may be reversed. In such situations,
 this document will be updated with information relevant to the decision.
-*However, the deprecation identifier will not be modified*.
+However, the deprecation identifier will not be modified.
 
 ## List of Deprecated APIs