Don't run the second part of XMLHTTPMessageTest>>#testAddHeader | #te…

…stHeaderValuesAdd when Pharo version is before 10 (needs the Zinc patch to ZnMultiValueDictionary that make #at:add idempotent for identical key/values)

src/XML-Parser-Tests/XMLHTTPMessageTest.class.st

@@ -101,6 +101,9 @@ XMLHTTPMessageTest >> testAddHeader [
 			assertMessage: message
 			hasHeaders: addedHeaders].
 
+	SystemVersion current major >= 10
+		ifFalse: [^ self].
+
 	self headers do: [:each |
 		self assert: (message addHeader: each) equals: each.
 		self
@@ -505,6 +508,9 @@ XMLHTTPMessageTest >> testHeaderValuesAtAdd [
 			assertMessage: message
 			hasHeaders: addedHeaders].
 
+	SystemVersion current major >= 10
+		ifFalse: [^ self].
+
 	self headers do: [:each |
 		self assert:
 			(message