Upgrading matplotlib to last stable version to support pytho 3.8 used on the test setups

Change-Id: I8abd62f7bd92eb4a3208510e42589a8063363c66
diff --git a/VERSION b/VERSION
index a4dd9db..a603bb5 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.7.4
+2.7.5