This can be removed in the Message Catalog Editor. Once it is removed, it will be a site wide change.
  1. Go to Setup > select Product Configuration
  2. Search for the word "dear"
  3. Under the Key column, look for confirmation_greeting
  4. Click Edit Custom
  5. Click Submit without entering anything in the text field
  6. This will remove this salutation
If your site uses multiple locales, you can select the various locals you wish to remove this from in the Language drop down, and repeat the steps above for all desired languages.