Use actualCustomStringRepresentation() when disambiguating based on equal toStrings().

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=143037531
diff --git a/core/src/main/java/com/google/common/truth/Subject.java b/core/src/main/java/com/google/common/truth/Subject.java
index 8cebff8..301ad19 100644
--- a/core/src/main/java/com/google/common/truth/Subject.java
+++ b/core/src/main/java/com/google/common/truth/Subject.java
@@ -319,7 +319,7 @@
     // If the subject and parts aren't null, and they have equal toString()'s but different
     // classes, we need to disambiguate them.
     boolean neitherNull = (other != null) && (subject != null);
-    boolean sameToStrings = neitherNull && subject.toString().equals(other.toString());
+    boolean sameToStrings = actualCustomStringRepresentation().equals(String.valueOf(other));
     boolean needsClassDisambiguation =
         neitherNull && sameToStrings && !subject.getClass().equals(other.getClass());
     if (needsClassDisambiguation) {