Update formatting of the status fields for SE-0141 and SE-0142.

"Under review" -> "Active review". Format the date using: (MONTH DAY...MONTH DAY)

Author: krilnon

proposals/0141-available-by-swift-version.md

@@ -3,7 +3,7 @@
 * Proposal: [SE-0141](0141-available-by-swift-version.md)
 * Authors: [Graydon Hoare](https://github.com/graydon)
 * Review Manager: [Doug Gregor](https://github.com/DougGregor)
-* Status: Under review (September 23...28, 2016)
+* Status: **Active review (September 23...September 28)**
 
 ## Introduction
 

proposals/0142-associated-types-constraints.md

@@ -3,7 +3,7 @@
 * Proposal: [SE-0142](0142-associated-types-constraints.md)
 * Authors: [David Hart](https://github.com/hartbit), [Jacob Bandes-Storch](https://github.com/jtbandes), [Doug Gregor](https://github.com/DougGregor)
 * Review Manager: [Doug Gregor](https://github.com/DougGregor)
-* Status: Under review (September 23...30, 2016)
+* Status: **Active review (September 23...September 30)**
 
 ## Introduction