Freezing matplotlib to 3.3.4

Change-Id: I44937fd9e7a8e4871a88d749a0141e03be96973a
diff --git a/requirements.txt b/requirements.txt
index 7952b24..233cf01 100755
--- a/requirements.txt
+++ b/requirements.txt
@@ -11,7 +11,7 @@
 git+https://github.com/zdw/robotframework-importresource@b81b87aabaee0594e966687b41e3674b866f28ee
 cord-robot==2.1.8
 virtualenv
-matplotlib==3.0.3
+matplotlib==3.3.4
 requests==2.24.0
 grpc-robot>=2.9.3
 kafka-robot>=2.3.2