Remove sig for IO#{ready?,nread}

These methods have been removed.
See also ruby/io-wait#49

Author: ksss

core/io/wait.rbs

@@ -1,26 +1,5 @@
 %a{annotate:rdoc:skip}
 class IO
-  # <!--
-  #   rdoc-file=ext/io/wait/wait.c
-  #   - io.nread -> int
-  # -->
-  # Returns number of bytes that can be read without blocking. Returns zero if no
-  # information available.
-  #
-  # You must require 'io/wait' to use this method.
-  #
-  def nread: () -> Integer
-
-  # <!--
-  #   rdoc-file=ext/io/wait/wait.c
-  #   - io.ready? -> truthy or falsy
-  # -->
-  # Returns a truthy value if input available without blocking, or a falsy value.
-  #
-  # You must require 'io/wait' to use this method.
-  #
-  def ready?: () -> boolish
-
   # <!--
   #   rdoc-file=ext/io/wait/wait.c
   #   - io.wait(events, timeout) -> event mask, false or nil

test/stdlib/IO_test.rb

@@ -525,26 +525,6 @@ class IOWaitTest < Test::Unit::TestCase
 
   testing "::IO"
 
-  def test_readyp
-    # This method returns true|false in Ruby 2.7, nil|IO in 3.0, and true|false in 3.1.
-
-    IO.pipe.tap do |r, w|
-      assert_send_type(
-        "() -> untyped",
-        r, :ready?
-      )
-    end
-
-    IO.pipe.tap do |r, w|
-      w.write("hello")
-
-      assert_send_type(
-        "() -> untyped",
-        r, :ready?
-      )
-    end
-  end
-
   def test_wait_readable
     if_ruby "3.0.0"..."3.2.0" do
       IO.pipe.tap do |r, w|
@@ -583,15 +563,6 @@ def test_wait_writable
     end
   end
 
-  def test_nread
-    IO.pipe.tap do |r, w|
-      assert_send_type(
-        "() -> Integer",
-        r, :nread
-      )
-    end
-  end
-
   def test_wait
     if_ruby "3.0.0"..."3.2.0", skip: false do
       IO.pipe.tap do |r, w|