Upgrading setuptools to 51.0.0

Some newer packages, in requirements.txt, use the Metadata
version format available in 51.0.0.

Docs: https://setuptools.readthedocs.io/en/latest/userguide/declarative_config.html#metadata

Change-Id: I2a7c22c2fa42e7111aed462b81f5be9040d0d7f9
Signed-off-by: sousaedu <eduardo.sousa@canonical.com>
diff --git a/docker/MON/Dockerfile b/docker/MON/Dockerfile
index 765324c..f619e97 100644
--- a/docker/MON/Dockerfile
+++ b/docker/MON/Dockerfile
@@ -30,7 +30,7 @@
     python3-setuptools=45.2.* \
     python3-dev=3.8.* \
     openssh-client=1:8.* && \
-    python3 -m easy_install pip==21.0.1
+    python3 -m easy_install pip==21.0.1 setuptools==51.0.0
 
 ARG PYTHON3_OSM_COMMON_URL
 ARG PYTHON3_OSM_MON_URL