Can I delete Siri from the Touch Bar?

Yes, you can remove the button.

Step 2 Remove buttons

Quoting from the below linked article:

Customize the Touch Bar

For some apps, you can customize the Touch Bar so that it contains buttons for your favorite tasks in that app. You can also change which buttons are shown in the Control Strip.

1. Choose View > Customize Touch Bar.
2. Add, rearrange, or remove buttons in the Touch Bar.
   To switch between changing buttons for the current app and the Control Strip, just tap the Touch Bar. (You can’t customize buttons for all apps.)

   Add buttons: Use the trackpad or mouse to drag a button from the screen to the Touch Bar; buttons in the Touch Bar jiggle slightly.

   Rearrange buttons: Use your finger on the Touch Bar to drag a button.

   Remove buttons: Use the trackpad or mouse to drag a button from the Touch Bar to the screen.

3. When you’re finished, click Done on the screen or tap Done in the Touch Bar.

You can also customize the Control Strip in System Preferences. Choose Apple menu > System Preferences, click Keyboard, click Keyboard, then click Customize Control Strip.

https://support.apple.com/kb/PH26221?viewlocale=en_US&locale=cs_CZ

Do you not see a section like this:

To elaborate on what Dominic said, you can actually just use the trackpad to do anything. If you drag the mouse pointer all the way to the bottom of the screen, the buttons on the touch bar should light up, then you can drag it over to where you want and drag up to remove. But even if you remove, the button buttons will slide to the right, and you'll still have a button above the delete key, there is currently no way to leave an empty space there as far as I know.