chore: update seconds per session for olv (#278)

Author: rachitm022

defaults/docs-defaults.yaml

@@ -52,7 +52,7 @@ defaults:
     linear-tv: 2580
     search: 120
     social: 240
-    streaming-video: 300
+    streaming-video: 143
     traditional-radio: 2580
     web: 320
   default_baseload_watts:

docs/snippets/defaults_channel_mapping.mdx

@@ -95,7 +95,7 @@ default_property_ad_funded_percentage_by_channel:
 default_average_seconds_per_session_excluding_ads_by_channel:
   social:   240
   ctv-bvod: 2580
-  streaming-video: 300
+  streaming-video: 143
   digital-audio:    1500
   app:      140
   web:      320