Fix formatting and grammar in PostHog setup guide

Corrected capitalization and punctuation in instructions.

Author: sade-wusi

src/connections/destinations/catalog/posthog/index.md

@@ -11,15 +11,15 @@ This destination is maintained by PostHog. For any issues with the destination,
 
 ## Getting started
 
-1. From the Destinations catalog page in the Segment App, click **Add Destination**.
+1. From the destinations catalog page in the Segment App, click **Add Destination**.
 2. Search for "PostHog" in the Destinations Catalog, and select the PostHog destination.
-3. Choose which Source should send data to the PostHog destination.
+3. Choose which source should send data to the PostHog destination.
 4. Go to your [PostHog project settings](https://us.posthog.com/settings/project#variables){:target="_blank"}, and copy the **project API key**.
 5. Enter the project API Key that you copied in the PostHog destination settings in Segment.
-6. Enter your PostHog instance address *without any trailing slash*, for example:
-    - `https://us.i.posthog.com` if you use PostHog US Cloud
-    - `https://eu.i.posthog.com` if you use PostHog EU Cloud
-    - Your self-hosted URL if you self-host
+6. Enter your PostHog instance address **without any trailing slash**, for example:
+    - `https://us.i.posthog.com` if you use PostHog US Cloud.
+    - `https://eu.i.posthog.com` if you use PostHog EU Cloud.
+    - Your self-hosted URL if you self-host.
 
 ## Page