Bump black from 24.3.0 to 26.3.1 in /.tools/readmes (#7773)

Author: dependabot[bot]

.tools/readmes/requirements_freeze.txt

@@ -1,5 +1,5 @@
 aws_doc_sdk_examples_tools @ git+https://github.com/awsdocs/aws-doc-sdk-examples-tools@2025.41.0
-black==24.3.0
+black==26.3.1
 certifi==2025.1.31
 charset-normalizer==3.4.1
 click==8.1.8