Improve where.not docs [ci skip]

* Fix example queries
* Remove doc entries of where.like/not_like.
* Remove :chain from where.not related docs. To me that's an implementation
  detail and we don't expect people to use where(:chain).not.

activerecord/lib/active_record/relation/query_methods.rb

@@ -18,13 +18,13 @@ module ActiveRecord
       # See #where for more details on each format.
       #
       #    User.where.not("name = 'Jon'")
-      #    # SELECT * FROM users WHERE name <> 'Jon'
+      #    # SELECT * FROM users WHERE NOT (name = 'Jon')
       #
       #    User.where.not(["name = ?", "Jon"])
-      #    # SELECT * FROM users WHERE name <> 'Jon'
+      #    # SELECT * FROM users WHERE NOT (name = 'Jon')
       #
       #    User.where.not(name: "Jon")
-      #    # SELECT * FROM users WHERE name <> 'Jon'
+      #    # SELECT * FROM users WHERE name != 'Jon'
       #
       #    User.where.not(name: nil)
       #    # SELECT * FROM users WHERE name IS NOT NULL
@@ -415,21 +415,15 @@ module ActiveRecord
     #    User.joins(:posts).where({ "posts.published" => true })
     #    User.joins(:posts).where({ posts: { published: true } })
     #
-    # === no argument or :chain
+    # === no argument
     #
-    # If no argument or :chain is passed, #where returns a new instance of WhereChain which, when
-    # chained with either #not, #like, or #not_like, returns a new relation.
+    # If no argument is passed, #where returns a new instance of WhereChain, that
+    # can be chained with #not to return a new relation that negates the where clause.
     #
     #    User.where.not(name: "Jon")
-    #    # SELECT * FROM users WHERE name <> 'Jon'
+    #    # SELECT * FROM users WHERE name != 'Jon'
     #
-    #    Book.where.like(title: "Rails%")
-    #    # SELECT * FROM books WHERE title LIKE 'Rails%'
-    #
-    #    Conference.where.not_like(name: "%Kaigi")
-    #    # SELECT * FROM conferences WHERE name NOT LIKE '%Kaigi'
-    #
-    # See WhereChain for more details on #not, #like, and #not_like.
+    # See WhereChain for more details on #not.
     #
     # === blank condition
     #