Update setup.py

PyYAML was also generating conflict

Author: afmurillo

setup.py

@@ -15,7 +15,7 @@
     license='MIT',
     packages=['dhalsim'],
     install_requires=[
-       'PyYAML',
+       'PyYAML==5.4.1',
         'pyyaml-include',
         'antlr4-python3-runtime==4.7.2',
         'progressbar2',