Update ruamel-yaml requirement

Updates the requirements on [ruamel-yaml](https://sourceforge.net/p/ruamel-yaml/code/ci/default/tree) to permit the latest version.

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

setup.py

@@ -25,7 +25,7 @@
       install_requires=[
           'future',
           'connexion >= 2.0.2, < 3',
-          'ruamel.yaml >= 0.12.4, <= 0.15.77',
+          'ruamel.yaml >= 0.12.4, < 0.16.11',
           'schema-salad',
           'subprocess32==3.5.2'
                         ],