Update to reflect Functions cost revamp. (#1490)

* Update to reflect Functions cost revamp.

Context to this change here: https://paper.dropbox.com/doc/Functions-Cost-Revamp-Comms--BH7qOC7L4LDruT5Hbd50LFu4Ag-UzTFL7IjG0r43dMi791ZO.

We will need to deploy this change on March 31 sometime before or at 5pm PST when the change will be deployed to the billing pipeline. @sanscontext let me know if you have any comments/edits and if it'd be possible for you to help us merge this at the appropriate time. Sorry for the late notice!

* Update src/connections/functions/usage.md

Co-authored-by: LRubin <[email protected]>

* Update src/connections/functions/usage.md

Co-authored-by: Chris O'Hara <[email protected]>

Co-authored-by: LRubin <[email protected]>
Co-authored-by: Chris O'Hara <[email protected]>
Co-authored-by: markzegarelli <[email protected]>

Author: 4 people

src/connections/functions/usage.md

@@ -14,7 +14,7 @@ The amount of time you are allotted changes depending on your [Segment pricing p
 
 We measure execution time from when the function first receives an event to the time the function either returns successfully or throws an error. If Segment retries your function (for example, if there was a timeout), those retries also count as billable execution time.
 
-Functions are billed in 100ms increments, rounded up. For example, a function that takes 80ms to complete will be billed as 100ms. A function that takes 105ms to complete will be billed as 200ms.
+Starting on April 8, 2021 Functions usage is measured in millisecond increments. This makes your usage and billing much more precise. Prior to this change, Functions was measured in 100ms increments, and then rounded up. For example, a function that took 80ms to complete was previously billed as 100ms. Using the new usage calculation, it is billed as 80ms. 
 
 ## Execution timeouts