Bump boto3 from 1.12.37 to 1.12.39 (#1476)

Bumps [boto3](https://github.com/boto/boto3) from 1.12.37 to 1.12.39.
- [Release notes](https://github.com/boto/boto3/releases)
- [Changelog](https://github.com/boto/boto3/blob/develop/CHANGELOG.rst)
- [Commits](https://github.com/boto/boto3/compare/1.12.37...1.12.39)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

requirements.txt

@@ -1,5 +1,5 @@
 adr==0.17.7
-boto3==1.12.37
+boto3==1.12.39
 imbalanced-learn==0.6.2
 joblib==0.14.1
 libmozdata==0.1.65