[ObjC] Typos and comment improvements.
diff --git a/objectivec/GPBUtilities.h b/objectivec/GPBUtilities.h
index 828fd16..75759b2 100644
--- a/objectivec/GPBUtilities.h
+++ b/objectivec/GPBUtilities.h
@@ -95,7 +95,7 @@
 void GPBClearMessageField(GPBMessage *self, GPBFieldDescriptor *field);
 
 /**
- * Clears the given onoof field for the given message.
+ * Clears the given oneof field for the given message.
  *
  * @param self  The message for which to clear the field.
  * @param oneof The oneof to clear.