Barnett: Update image credits. (#5386)

* Barnett: Update image credits.

* Remove credit from style.css

Co-authored-by: Ben Dwyer <ben@scruffian.com>

barnett/readme.txt

@@ -32,6 +32,6 @@ GNU General Public License for more details.
 
 Barnett uses the following third-party resources:
 
-Green tropical leaves background. Original public domain image from Wikimedia Commons.
-Source: https://www.rawpixel.com/image/3286299/free-photo-image-flower-tropical-green
+Space Travel Poster (2015). Original from Official SpaceX Photos. Digitally enhanced by rawpixel.
+Source: https://www.rawpixel.com/image/2257682/spacex-travel-poster
 Used in theme screenshot and demo site.

barnett/style.css

@@ -26,11 +26,4 @@ This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 GNU General Public License for more details.
-
-Barnett uses the following third-party resources:
-
-Green tropical leaves background. Original public domain image from Wikimedia Commons.
-Source: https://www.rawpixel.com/image/3286299/free-photo-image-flower-tropical-green
-Used in theme screenshot and demo site.
-
-*/
+*/