[gimp-macos-build] use python 3.6 instead

[Alex Samorukov <asamorukov src gnome org>]

commit 309abaecd736829e9ee5df0fdcdf12c8521393ad
Author: Oleksii Samorukov <oleksii_samorukov mckinsey com>
Date:   Sat Oct 26 22:57:19 2019 +0200

    use python 3.6 instead

 .circleci/config.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/.circleci/config.yml b/.circleci/config.yml
index 7bfc531..3555dfa 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -24,8 +24,8 @@ jobs:
             name: Setup Python3
             command: |
               cd ~/
-              curl -L 'https://www.python.org/ftp/python/3.8.0/python-3.8.0-macosx10.9.pkg' > 
python-3.8.0-macosx10.9.pkg
-              sudo installer -pkg python-3.8.0-macosx10.9.pkg -target /
+              curl -L 'https://www.python.org/ftp/python/3.6.8/python-3.6.8-macosx10.9.pkg' > 
python-3.6.8-macosx10.9.pkg
+              sudo installer -pkg python-3.6.8-macosx10.9.pkg -target /
         - run:
             name: Setup 10.9 SDK
             command: |