FB Conversions API copy edits (#1417)

* copy edit and clarify
Added  a "Set up in Facebook" section
Added  a "For New Pixels" subsection
Added  a "For Existing Pixels" subsection (Both of these subsections share the same last two steps - maybe there is a cleaner approach?)
Modified the info panel to refer to the "Configuration options" section instead of the "Use Cases" section

Co-authored-by: James Reynolds <[email protected]>

Author: sanscontext

src/_data/catalog/destinations.yml

@@ -1,5 +1,5 @@
 # AUTOGENERATED FROM PLATFORM API. DO NOT EDIT
-# destination data last updated 2021-02-12 
+# destination data last updated 2021-02-16 
 items:
 - display_name: ActiveCampaign
   slug: activecampaign
@@ -3073,7 +3073,7 @@ items:
     deprecated: false
     required: true
     string_validators:
-      regexp: ''
+      regexp: '^https://'
     description: >-
       The URL to call the Function. It must follow the ` https://{function app
       name}.azurewebsites.net/api/{function name}?code={function key}` pattern.
@@ -10147,7 +10147,7 @@ items:
     deprecated: false
     required: true
     string_validators:
-      regexp: ''
+      regexp: '^https://'
     description: The URL to call the Google Cloud Function.
     settings: []
   connection_modes:

src/connections/destinations/catalog/facebook-conversions-api/index.md

@@ -2,4 +2,7 @@
 title: 'Facebook Conversions API Destination'
 hidden: true
 beta: true
----
+---
+
+<!-- LR: 2/16/2021: Redirects to /docs/connections/destinations/catalog/facebook-pixel-server-side
+because while this destination's display name has changed, the slug is still the old name and the docs build needs to match on slug to find it in `destinations.yml` -->