Change the pending with block error message

We used to mention RSpec 2 there which is long gone.

Also, this note was misleading:

> If you want to declare an example `pending` and bypass the `before`
hooks as well, you can pass `:pending => true`

In the following spec:

    RSpec.describe do
      before { puts 'before!' }

      it do
        pending 'oops'
        fail 'djosdkfjos'
      end

      it 'pending metadata', pending: true do
        fail 'dferrerere'
      end
    end

the hook is run for both metadata and in-example `pending`:

    before!
      pending metadata (PENDING: No reason given)
    before!
      example at ./spec/a_spec.rb:4 (PENDING: oops)

Author: pirj

lib/rspec/core/pending.rb

@@ -51,36 +51,12 @@ class PendingExampleFixedError < StandardError; end
       #         raise "broken"
       #       end
       #     end
-      #
-      # @note `before(:example)` hooks are eval'd when you use the `pending`
-      #   method within an example. If you want to declare an example `pending`
-      #   and bypass the `before` hooks as well, you can pass `:pending => true`
-      #   to the `it` method:
-      #
-      #       it "does something", :pending => true do
-      #         # ...
-      #       end
-      #
-      #   or pass `:pending => "something else getting finished"` to add a
-      #   message to the summary report:
-      #
-      #       it "does something", :pending => "something else getting finished" do
-      #         # ...
-      #       end
       def pending(message=nil)
         current_example = RSpec.current_example
 
         if block_given?
           raise ArgumentError, <<-EOS.gsub(/^\s+\|/, '')
-            |The semantics of `RSpec::Core::Pending#pending` have changed in
-            |RSpec 3. In RSpec 2.x, it caused the example to be skipped. In
-            |RSpec 3, the rest of the example is still run but is expected to
-            |fail, and will be marked as a failure (rather than as pending) if
-            |the example passes.
-            |
-            |Passing a block within an example is now deprecated. Marking the
-            |example as pending provides the same behavior in RSpec 3 which was
-            |provided only by the block in RSpec 2.x.
+            |Passing a block within an example is not supported.
             |
             |Move the code in the block provided to `pending` into the rest of
             |the example body.

spec/rspec/core/example_spec.rb

@@ -744,7 +744,7 @@ def expect_pending_result(example)
         group.run
         expect(example).to fail_with ArgumentError
         expect(example.exception.message).to match(
-          /Passing a block within an example is now deprecated./
+          /Passing a block within an example is not supported./
         )
       end
     end

spec/rspec/core/pending_example_spec.rb

@@ -200,7 +200,7 @@
       group.run
       expect(example).to fail_with ArgumentError
       expect(example.exception.message).to match(
-        /Passing a block within an example is now deprecated./
+        /Passing a block within an example is not supported./
       )
     end