fix AS/core_ext examples [ci skip]

activesupport/lib/active_support/core_ext/hash/indifferent_access.rb

@@ -4,7 +4,7 @@ class Hash
 
   # Returns an <tt>ActiveSupport::HashWithIndifferentAccess</tt> out of its receiver:
   #
-  #   { a: 1}.with_indifferent_access['a'] # => 1
+  #   { a: 1 }.with_indifferent_access['a'] # => 1
   def with_indifferent_access
     ActiveSupport::HashWithIndifferentAccess.new_from_hash_copying_default(self)
   end

activesupport/lib/active_support/core_ext/hash/keys.rb

@@ -63,7 +63,7 @@ class Hash
   #
   #   { name: 'Rob', years: '28' }.assert_valid_keys(:name, :age) # => raises "ArgumentError: Unknown key: years"
   #   { name: 'Rob', age: '28' }.assert_valid_keys('name', 'age') # => raises "ArgumentError: Unknown key: name"
-  #   { name: 'Rob', age: '28' }.assert_valid_keys(:name, :age) # => passes, raises nothing
+  #   { name: 'Rob', age: '28' }.assert_valid_keys(:name, :age)   # => passes, raises nothing
   def assert_valid_keys(*valid_keys)
     valid_keys.flatten!
     each_key do |k|

activesupport/lib/active_support/core_ext/hash/reverse_merge.rb

@@ -5,7 +5,7 @@ class Hash
   #
   # is equivalent to
   #
-  #   options = { size: 25, velocity: 10}.merge(options)
+  #   options = { size: 25, velocity: 10 }.merge(options)
   #
   # This is particularly useful for initializing an options hash
   # with default values.