Rollback as osx build not available for latest

Author: Thrameos

.azure/scripts/osx-python.sh

@@ -4,10 +4,10 @@ PYTHON_VERSION="$1"
 
 case $PYTHON_VERSION in
 3.6)
-  FULL_VERSION=3.6.10
+  FULL_VERSION=3.6.8
   ;;
 3.7)
-  FULL_VERSION=3.7.11
+  FULL_VERSION=3.7.9
   ;;
 3.8)
   FULL_VERSION=3.8.6