Fix grammar in Range docs (#10851)

- Use "with a step of X"
- Replace usage of "start" and "stop" with "first" and "last"

Author: eksperimental

lib/elixir/lib/calendar/date.ex

@@ -92,7 +92,7 @@ defmodule Date do
   def range(%{calendar: calendar} = first, %{calendar: calendar} = last) do
     {first_days, _} = to_iso_days(first)
     {last_days, _} = to_iso_days(last)
-    # TODO: Deprecate inferring a range with step of -1 on Elixir v1.16
+    # TODO: Deprecate inferring a range with a step of -1 on Elixir v1.16
     step = if first_days <= last_days, do: 1, else: -1
     range(first, first_days, last, last_days, calendar, step)
   end
@@ -102,7 +102,7 @@ defmodule Date do
   end
 
   @doc """
-  Returns a range of dates with step.
+  Returns a range of dates with a step.
 
   ## Examples
 

lib/elixir/lib/kernel.ex

@@ -3673,7 +3673,7 @@ defmodule Kernel do
   end
 
   defp range(_context, first, last) when is_integer(first) and is_integer(last) do
-    # TODO: Deprecate inferring a range with step of -1 on Elixir v1.17
+    # TODO: Deprecate inferring a range with a step of -1 on Elixir v1.17
     step = if first <= last, do: 1, else: -1
     {:%{}, [], [__struct__: Elixir.Range, first: first, last: last, step: step]}
   end

lib/elixir/lib/range.ex

@@ -29,10 +29,10 @@ defmodule Range do
       iex> Enum.to_list(0..10//-1)
       []
 
-  When defining a range without steps, the step will be
-  defined based on the start and stop position of the
-  range, If `start >= stop`, it will be an increasing range
-  with step of 1. Otherwise, it is a decreasing range.
+  When defining a range without a step, the step will be
+  defined based on the first and last position of the
+  range, If `first >= last`, it will be an increasing range
+  with a step of 1. Otherwise, it is a decreasing range.
   Note however implicitly decreasing ranges are deprecated.
   Therefore, if you need a decreasing range from `3` to `1`,
   prefer to write `3..1//-1` instead.
@@ -120,7 +120,7 @@ defmodule Range do
 
   @spec new(limit, limit) :: t
   def new(first, last) when is_integer(first) and is_integer(last) do
-    # TODO: Deprecate inferring a range with step of -1 on Elixir v1.17
+    # TODO: Deprecate inferring a range with a step of -1 on Elixir v1.17
     step = if first <= last, do: 1, else: -1
     %Range{first: first, last: last, step: step}
   end