Remove duplicate boto3 requirement

There is a boto3 requirement in requirements.txt and in tests/requirements.txt. This will eventually lead to some confusion because it's prone to get out of sync. It is a core dependency, so I kept it in requirements.txt.

tests/requirements.txt

@@ -1,4 +1,3 @@
-boto3>=1.26.110
 detect-secrets>=1.3.0
 flake8>=5.0.4
 httpx>=0.24.1