Issue #1647: Fix String#pp output color

This commit fixes #1647 and pretty prints strings in red instead of
green. This bug was introduced in https://github.com/pry/pry/pull/1586.
It will also continue to pretty print multi-line strings without a '+'
delimiter, per the same pull request.

lib/pry/color_printer.rb

@@ -32,9 +32,7 @@ class Pry
 
     def pp(obj)
       if String === obj
-        # Avoid calling Ruby 2.4+ String#pretty_print that prints multiline
+        text(obj.inspect)
-        # Strings prettier
-        Object.instance_method(:pretty_print).bind(obj).call
       else
         super
       end

spec/color_printer_spec.rb

@@ -80,5 +80,21 @@ describe Pry::ColorPrinter do
         expect(str).to match(/\A#<BasicG:0x\w+>\z/)
       end
     end
+
+    describe 'String' do
+      context 'with a single-line string' do
+        it 'pretty prints the string' do
+          Pry::ColorPrinter.pp('hello world', io)
+          expect(str).to eq('"hello world"')
+        end
+      end
+
+      context 'with a multi-line string' do
+        it 'pretty prints the string' do
+          Pry::ColorPrinter.pp("hello\nworld", io)
+          expect(str).to eq('"hello\nworld"')
+        end
+      end
+    end
   end
 end