Fix grammar and diction of NOR conditions warning message

activerecord/lib/active_record/relation/query_methods.rb

@@ -51,7 +51,7 @@ def not(opts, *rest)
         if not_behaves_as_nor?(opts)
           ActiveSupport::Deprecation.warn(<<~MSG.squish)
             NOT conditions will no longer behave as NOR in Rails 6.1.
-            To continue using NOR conditions, NOT each conditions manually
+            To continue using NOR conditions, NOT each condition individually
             (`#{
               opts.flat_map { |key, value|
                 if value.is_a?(Hash) && value.size > 1

activerecord/test/cases/relation/where_test.rb

@@ -167,7 +167,7 @@ def test_where_not_polymorphic_id_and_type_as_nor_is_deprecated
 
       message = <<~MSG.squish
         NOT conditions will no longer behave as NOR in Rails 6.1.
-        To continue using NOR conditions, NOT each conditions manually
+        To continue using NOR conditions, NOT each condition individually
         (`.where.not(:estimate_of_type => ...).where.not(:estimate_of_id => ...)`).
       MSG
       actual = assert_deprecated(message) do
@@ -188,7 +188,7 @@ def test_where_not_association_as_nor_is_deprecated
 
       message = <<~MSG.squish
         NOT conditions will no longer behave as NOR in Rails 6.1.
-        To continue using NOR conditions, NOT each conditions manually
+        To continue using NOR conditions, NOT each condition individually
         (`.where.not(:price_estimates => { :price => ... }).where.not(:price_estimates => { :currency => ... })`).
       MSG
       assert_deprecated(message) do