Fixed typo, as per PR review

Author: lposen

example/.env.example

@@ -6,7 +6,7 @@
 #  1. Sign into your Iterable account
 #  2. Go to [Integrations > API Keys](https://app.iterable.com/settings/apiKeys)
 #  3. Click "New API Key" in the top right corner
-#  4. Fill in the followsing fields:
+#  4. Fill in the following fields:
 #     - Name: A descriptive name for the API key
 #     - Type: Mobile
 #     - JWT authentication: Leave **unchecked** (IMPORTANT)