Adjust docs of create_or_find_by

- Mention explicitly in the docs that `create_of_find_by` requires a DB
constraint.

Closes rails#36027

Co-authored-by: Eileen M. Uchitelle <[email protected]>

Author: intrip

activerecord/lib/active_record/relation.rb

@@ -182,7 +182,7 @@ def find_or_create_by!(attributes, &block)
       find_by(attributes) || create!(attributes, &block)
     end
 
-    # Attempts to create a record with the given attributes in a table that has a unique constraint
+    # Attempts to create a record with the given attributes in a table that has a unique database constraint
     # on one or several of its columns. If a row already exists with one or several of these
     # unique constraints, the exception such an insertion would normally raise is caught,
     # and the existing record with those attributes is found using #find_by!.
@@ -193,7 +193,7 @@ def find_or_create_by!(attributes, &block)
     #
     # There are several drawbacks to #create_or_find_by, though:
     #
-    # * The underlying table must have the relevant columns defined with unique constraints.
+    # * The underlying table must have the relevant columns defined with unique database constraints.
     # * A unique constraint violation may be triggered by only one, or at least less than all,
     #   of the given attributes. This means that the subsequent #find_by! may fail to find a
     #   matching record, which will then raise an <tt>ActiveRecord::RecordNotFound</tt> exception,