Fix typo /a HTTP/an HTTP/ [ci skip]

Follow up #37281.

activestorage/app/models/active_storage/blob.rb

@@ -220,7 +220,7 @@ def delete
   end
 
   # Deletes the file on the service and then destroys the blob record. This is the recommended way to dispose of unwanted
-  # blobs. Note, though, that deleting the file off the service will initiate a HTTP connection to the service, which may
+  # blobs. Note, though, that deleting the file off the service will initiate an HTTP connection to the service, which may
   # be slow or prevented, so you should not use this method inside a transaction or in callbacks. Use #purge_later instead.
   def purge
     destroy