Fix version tox in container

Related-prod: PRODX-3058
Change-Id: I02bd04165398808a3aef3b53a2ed51d311cc7b95
diff --git a/Dockerfile b/Dockerfile
index efb07ee..22e7e3e 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -16,7 +16,6 @@
     python3-pip \
     firefox \
     xvfb \
-    tox \
     wget \
     git \
     x11-xkb-utils
@@ -30,5 +29,5 @@
 
 WORKDIR /opt/horizon
 
-RUN pip3 install -r requirements.txt -r test-requirements.txt
+RUN pip3 install tox -U -r requirements.txt -r test-requirements.txt