[Diagnostics] Update educational note for AsyncCallerExecution feature to match @execution attribute split

Author: xedin

userdocs/diagnostics/async-caller-execution.md

@@ -7,9 +7,9 @@ these functions.
 
 This feature was proposed in [SE-0461](https://github.com/swiftlang/swift-evolution/blob/main/proposals/0461-async-function-isolation.md)
 
-* The `@execution(concurrent)` attribute specifies that a function must always 
+* The `@concurrent` attribute specifies that a function must always 
   switch off of an actor to run.
   This is the default behavior without `AsyncCallerExecution`.
-* The `@execution(caller)` attribute specifies that a function must always 
+* The `nonisolated(nonsending)` modifier specifies that a function must always 
   run on the caller's actor.
   This is the default behavior with `AsyncCallerExecution`.