Clarify upgrade path for Regex.regex? (#12785) (#12786)

Author: thbar

lib/elixir/lib/regex.ex

@@ -299,7 +299,7 @@ defmodule Regex do
  end
 
  @doc false
- @deprecated "Use Kernel.is_struct/2 or pattern match on %Regex{} instead"
+ @deprecated "Use Kernel.is_struct(term, Regex) or pattern match on %Regex{} instead"
  def regex?(term)
  def regex?(%Regex{}), do: true
  def regex?(_), do: false

lib/elixir/pages/references/compatibility-and-deprecations.md

@@ -82,7 +82,7 @@ Version | Deprecated feature | Replaced by (ava
 :-------| :-------------------------------------------------- | :---------------------------------------------------------------
 [v1.15] | `Calendar.ISO.day_of_week/3` | `Calendar.ISO.day_of_week/4` (v1.11)
 [v1.15] | `Exception.exception?/1` | `Kernel.is_exception/1` (v1.11)
-[v1.15] | `Regex.regex?/1` | `Kernel.is_struct/2` (v1.11)
+[v1.15] | `Regex.regex?/1` | `Kernel.is_struct/2` (`Kernel.is_struct(term, Regex)`) (v1.11)
 [v1.15] | `Logger.warn/2` | `Logger.warning/2` (v1.11)
 [v1.14] | `use Bitwise` | `import Bitwise` (v1.0)
 [v1.14] | `~~~/1` | `bnot/2` (v1.0)