Don't run on Mono

Author: slozier

tests/IronPython.Tests/Cases/IronPythonCasesManifest.ini

@@ -67,6 +67,8 @@ Reason=Assertion error
 
 [IronPython.test_memory]
 IsolationLevel=PROCESS # to avoid having a long list of object subtypes
+RunCondition=NOT $(IS_MONO)
+Reason=Memory allocation on Mono may not match MS.NET
 
 [IronPython.test_number]
 Timeout=300000 # 5 minute timeout - slow on macOS