Fix active_record_validations.md document, `:save` for `on:` validation helper was never available

According to the guide, ":save" value for the "on:" validation helper
was available like below

    validates :name, presence: true, on: :save

but this was never available according to the implementation of the
valid? method, which is below

    # Runs all the validations within the specified context. Returns
+true+ if
    # no errors are found, +false+ otherwise.
    #
    # If the argument is +false+ (default is +nil+), the context is set
to <tt>:create</tt> if
    # <tt>new_record?</tt> is +true+, and to <tt>:update</tt> if it is
not.
    #
    # Validations with no <tt>:on</tt> option will run no matter the
context. Validations with
    # some <tt>:on</tt> option will only run in the specified context.
    def valid?(context = nil)
      context ||= (new_record? ? :create : :update)
      output = super(context)
      errors.empty? && output
    end

So the documentation was always wrong since the PR proposed by
@neerajdotname  ( #10287 ) was rejected.

1 files changed, 2 insertions, 3 deletions

diff --git a/guides/source/active_record_validations.md b/guides/source/active_record_validations.md
index d95b587e78..8154d4e1cc 100644
--- a/guides/source/active_record_validations.md
+++ b/guides/source/active_record_validations.md
@@ -243,7 +243,7 @@ line of code you can add the same kind of validation to several attributes.
 All of them accept the `:on` and `:message` options, which define when the
 validation should be run and what message should be added to the `errors`
 collection if it fails, respectively. The `:on` option takes one of the values
-`:save` (the default), `:create` or `:update`. There is a default error
+`:create` or `:update`. There is a default error
 message for each one of the validation helpers. These messages are used when
 the `:message` option isn't specified. Let's take a look at each one of the
 available helpers.
@@ -765,10 +765,9 @@ class Person < ActiveRecord::Base
   validates :age, numericality: true, on: :update
 
   # the default (validates on both create and update)
-  validates :name, presence: true, on: :save
+  validates :name, presence: true
 end
 ```
-The last line is in review state and as of now, it is not running in any version of Rails 3.2.x as discussed in this [issue](https://github.com/rails/rails/issues/10248)
 
 Strict Validations
 ------------------