Fix wording of error message

at least I do not think "process" made sense here, when it is about handles/streams

src/core/Proc/Async.pm

@@ -8,7 +8,7 @@ my class X::Proc::Async::TapBeforeSpawn is Exception {
 my class X::Proc::Async::CharsOrBytes is Exception {
     has $.handle;
     method message() {
-        "Can only tap one of chars or bytes supply for process $!handle"
+        "Can only tap one of chars or bytes supply for $!handle"
     }
 }