Remove unnecessary link markup [ci-skip]

Because they are CamelCase, RDoc will automatically link these
references.  Automatic links have monospace formatting, whereas, in some
cases, manual links do not.

Author: jonathanhefner

actiontext/lib/action_text/fixture_set.rb

@@ -4,8 +4,7 @@ module ActionText
   # Fixtures are a way of organizing data that you want to test against; in
   # short, sample data.
   #
-  # To learn more about fixtures, read the
-  # {ActiveRecord::FixtureSet}[rdoc-ref:ActiveRecord::FixtureSet] documentation.
+  # To learn more about fixtures, read the ActiveRecord::FixtureSet documentation.
   #
   # === YAML
   #

activerecord/lib/active_record/transactions.rb

@@ -99,7 +99,7 @@ module Transactions
     # be propagated (after triggering the ROLLBACK), so you should be ready to
     # catch those in your application code.
     #
-    # One exception is the {ActiveRecord::Rollback}[rdoc-ref:Rollback] exception, which will trigger
+    # One exception is the ActiveRecord::Rollback exception, which will trigger
     # a ROLLBACK when raised, but not be re-raised by the transaction block. Any
     # other exception will be re-raised.
     #

activestorage/app/models/active_storage/attachment.rb

@@ -6,7 +6,7 @@
 # but it is possible to associate many different records with the same blob. A foreign-key constraint
 # on the attachments table prevents blobs from being purged if they’re still attached to any records.
 #
-# Attachments also have access to all methods from {ActiveStorage::Blob}[rdoc-ref:ActiveStorage::Blob].
+# Attachments also have access to all methods from ActiveStorage::Blob.
 #
 # If you wish to preload attachments or blobs, you can use these scopes:
 #

activestorage/lib/active_storage/fixture_set.rb

@@ -7,16 +7,13 @@ module ActiveStorage
   # Fixtures are a way of organizing data that you want to test against; in
   # short, sample data.
   #
-  # To learn more about fixtures, read the
-  # {ActiveRecord::FixtureSet}[rdoc-ref:ActiveRecord::FixtureSet] documentation.
+  # To learn more about fixtures, read the ActiveRecord::FixtureSet documentation.
   #
   # === YAML
   #
-  # Like other Active Record-backed models,
-  # {ActiveStorage::Attachment}[rdoc-ref:ActiveStorage::Attachment] and
-  # {ActiveStorage::Blob}[rdoc-ref:ActiveStorage::Blob] records inherit from
-  # {ActiveRecord::Base}[rdoc-ref:ActiveRecord::Base] instances and therefore
-  # can be populated by fixtures.
+  # Like other Active Record-backed models, ActiveStorage::Attachment and
+  # ActiveStorage::Blob records inherit from ActiveRecord::Base instances and
+  # therefore can be populated by fixtures.
   #
   # Consider a hypothetical <tt>Article</tt> model class, its related
   # fixture data, as well as fixture data for related ActiveStorage::Attachment