ConfiguredTargetFunction: remove debug marker

The change of the user-visible error message was introduced in 904a8d63833301f54c7df85bccc56ff67156afc5,
apparently by accident when doing further debugging after the review. Remove this marker as it
is not useful for the user.

Change-Id: I4455823597249820432fee7e366d0f6e70dc9bb2
PiperOrigin-RevId: 259319147
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/ConfiguredTargetFunction.java b/src/main/java/com/google/devtools/build/lib/skyframe/ConfiguredTargetFunction.java
index d674b5c..734f09b 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/ConfiguredTargetFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/ConfiguredTargetFunction.java
@@ -380,7 +380,7 @@
                 .handle(
                     Event.error(
                         String.format(
-                            "XXX - While resolving toolchains for target %s: %s",
+                            "While resolving toolchains for target %s: %s",
                             target.getLabel(), e.getCause().getMessage())));
           }
         }