docs: move ttshivers to Emeritus

Author: MikeMcC399

README.md

@@ -335,7 +335,6 @@ for project roles and decision-making, and [CONTRIBUTING.md](CONTRIBUTING.md) fo
 ### Collaborators
 
 - Tianon Gravi ([tianon](https://github.com/tianon))
-- ttshivers ([ttshivers](https://github.com/ttshivers))
 - [yosifkit](https://github.com/yosifkit)
 - Stewart X Addison ([sxa](https://github.com/sxa))
 - Mike McCready ([MikeMcC399](https://github.com/MikeMcC399))
@@ -353,3 +352,7 @@ Collaborators are managed via the
 - Peter Petrov ([pesho](https://github.com/pesho))
 - John Mitchell ([jlmitch5](https://github.com/jlmitch5))
 - Hugues Malphettes ([hmalphettes](https://github.com/hmalphettes))
+
+#### Former Collaborators
+
+- ttshivers ([ttshivers](https://github.com/ttshivers))