Move "avoid N+1 queries" explanation lower in the Active Storage documentation

The explanations about avoinding N+1 queries seems out of place early in
the documentation. The actual association hasn't been explained yet and
yet we explain performance optimizations.
It's also confusing when reading the following paragraph where "this
relationship" might seem to refer to the `with_attached_avatar` scope.

Instead we can group it as a performance section together with the
`strict_loading` section.

Author: p8

activestorage/lib/active_storage/attached/model.rb

@@ -61,10 +61,6 @@ module Attached::Model
       # There is no column defined on the model side, Active Storage takes
       # care of the mapping between your records and the attachment.
       #
-      # To avoid N+1 queries, you can include the attached blobs in your query like so:
-      #
-      #   User.with_attached_avatar
-      #
       # Under the covers, this relationship is implemented as a +has_one+ association to a
       # ActiveStorage::Attachment record and a +has_one-through+ association to a
       # ActiveStorage::Blob record. These associations are available as +avatar_attachment+
@@ -94,6 +90,10 @@ module Attached::Model
       #     has_one_attached :avatar, service: ->(user) { user.in_europe_region? ? :s3_europe : :s3_usa }
       #   end
       #
+      # To avoid N+1 queries, you can include the attached blobs in your query like so:
+      #
+      #   User.with_attached_avatar
+      #
       # If you need to enable +strict_loading+ to prevent lazy loading of attachment,
       # pass the +:strict_loading+ option. You can do:
       #
@@ -163,10 +163,6 @@ def #{name}=(attachable)
       # There are no columns defined on the model side, Active Storage takes
       # care of the mapping between your records and the attachments.
       #
-      # To avoid N+1 queries, you can include the attached blobs in your query like so:
-      #
-      #   Gallery.where(user: Current.user).with_attached_photos
-      #
       # Under the covers, this relationship is implemented as a +has_many+ association to a
       # ActiveStorage::Attachment record and a +has_many-through+ association to a
       # ActiveStorage::Blob record. These associations are available as +photos_attachments+
@@ -196,6 +192,10 @@ def #{name}=(attachable)
       #     has_many_attached :photos, service: ->(gallery) { gallery.personal? ? :personal_s3 : :s3 }
       #   end
       #
+      # To avoid N+1 queries, you can include the attached blobs in your query like so:
+      #
+      #   Gallery.where(user: Current.user).with_attached_photos
+      #
       # If you need to enable +strict_loading+ to prevent lazy loading of attachments,
       # pass the +:strict_loading+ option. You can do:
       #