[vulnerability] fix dependency (#10914)

this PR fixes https://github.com/huggingface/transformers/security/dependabot/examples/research_projects/lxmert/requirements.txt/PyYAML/open
2021-03-26 06:06:11 -07:00 · 2021-03-26 06:06:11 -07:00 · 3c27d246e5
--- a/examples/research_projects/lxmert/requirements.txt
+++ b/examples/research_projects/lxmert/requirements.txt
@ -70,7 +70,7 @@ pyrsistent==0.16.0
 python-dateutil==2.8.1
 pytoml==0.1.21
 pytz==2020.1
-PyYAML==5.3.1
+PyYAML>=5.4
 pyzmq==19.0.2
 qtconsole==4.7.7
 QtPy==1.9.0