Fix a few rubocop violations

come across these while reading code/specs

spec/rspec/core_spec.rb

@@ -98,7 +98,7 @@
   describe ".configure" do
     it "yields the current configuration" do
       RSpec.configure do |config|
-        expect(config).to equal(RSpec::configuration)
+        expect(config).to equal(RSpec.configuration)
       end
     end
   end
@@ -141,11 +141,11 @@
     end
 
     it 'removes the previously assigned example group constants' do
-        RSpec.describe "group"
+      RSpec.describe "group"
 
-        expect {
-          RSpec.world.reset
-        }.to change(RSpec::ExampleGroups, :constants).to([])
+      expect {
+        RSpec.world.reset
+      }.to change(RSpec::ExampleGroups, :constants).to([])
     end
   end
 
@@ -256,7 +256,7 @@ def reporter
 
       RSpec.clear_examples
 
-      RSpec.configuration.deprecation_stream = StringIO.new(deprecations = "".dup)
+      RSpec.configuration.deprecation_stream = StringIO.new(deprecations = +"")
 
       RSpec.describe do
         example { RSpec.deprecate("second deprecation") }
@@ -270,7 +270,7 @@ def reporter
     end
 
     it 'does not clear shared examples' do
-      RSpec.shared_examples_for("shared") { }
+      RSpec.shared_examples_for("shared") {}
 
       RSpec.clear_examples
 
@@ -281,8 +281,8 @@ def reporter
 
   it 'uses only one thread local variable', :run_last do
     # Trigger features that use thread locals...
-    aggregate_failures { }
-    RSpec.shared_examples_for("something") { }
+    aggregate_failures {}
+    RSpec.shared_examples_for("something") {}
 
     expect(Thread.current.keys.map(&:to_s).grep(/rspec/i).count).to eq(1)
   end
@@ -325,4 +325,3 @@ def reporter
     expect(status.exitstatus).to eq(0)
   end
 end
-