Fix for pyarmnn py35 Unit Tests

* py35 unit tests require more-itertools 8.10.0 as latest version 8.11.0
  breaks with py35

Signed-off-by: Kevin May <kevin.may@arm.com>
Change-Id: I21654fc73a3e3e9d00b14119eb840df750c81b12
diff --git a/python/pyarmnn/tox.ini b/python/pyarmnn/tox.ini
index 7fa437c..f791dba 100644
--- a/python/pyarmnn/tox.ini
+++ b/python/pyarmnn/tox.ini
@@ -13,6 +13,7 @@
        numpy==1.17.2
        pillow==6.1.0
        requests==2.23.0
+       more-itertools==8.10.0
 
 recreate = True
 whitelist_externals = /bin/sh