Fix tests to actually test when a image is set in config and first image is enabled

Author: ItayZiv

tests/roots/test-image-rel-paths/conf.py

@@ -7,4 +7,5 @@
 
 ogp_site_name = "Example's Docs!"
 ogp_site_url = "http://example.org/en/latest/"
+ogp_image = "_static/image33.png"
 ogp_use_first_image = True