replace new homepage hero, remove unused old homepage hero images (#207)

Author: mmeigs

source/generative-ai-faq.txt

@@ -8,7 +8,7 @@
 Generative AI FAQs
 ==================
 
-.. image:: /images/homepage-hero-revert.svg
+.. image:: /images/homepage-hero.svg
    :class: hero-img
    :alt: Homepage illustration
 

source/images/homepage-hero-revert.svg

@@ -22,7 +22,7 @@ MongoDB Documentation
    knowledge needed to build applications on MongoDB and 
    the Atlas developer data platform.
 
-.. image:: /images/homepage-hero-revert.svg
+.. image:: /images/homepage-hero.svg
    :class: hero-img
    :alt: Homepage illustration