Version bump

changelog.md

 # Changelog for [`process` package](http://hackage.haskell.org/package/process)
 
+## 1.6.13.1 *July 2021*
+
+* Patches for the previous release
+
 ## 1.6.13.0 *July 2021*
 
 * Refactoring of POSIX process logic [#208](https://github.com/haskell/process/pull/208)

process.cabal

 name:          process
-version:       1.6.13.0
+version:       1.6.13.1
 -- NOTE: Don't forget to update ./changelog.md
 license:       BSD3
 license-file:  LICENSE