terminology fixes

Author: swapdisk

docs/source/_static/images/inplace-upgrade-workflow.svg

@@ -39,7 +39,7 @@ Stage is a part of a [phase](#phase). There are three defined stages:
 - Main
 - After
 
-Before and After phases can be used to allow an actor to be run before or after any
+Before and After stages can be used to allow an actor to be run before or after any
 other actors in the phase. This should be useful in some hooking scenarios, where
 an action is supposed to be happening before or after another action. This way, other
 actors could be influenced.
@@ -63,4 +63,4 @@ the repositories on the system.
 
 Workflow APIs are custom API classes that actors can use and automatically inherit their consumed and produced
 messages. This way one can write a stable API for third party actor writers, without being affected by changes of
-message model layout, name changes etc.
+message model layout, name changes etc.