Update python-libjuju version to 2.9.42.4

Change-Id: Ie9b42f14c59aa9690afde319e29cebbf3de173b1
Signed-off-by: Guillermo Calvino <guillermo.calvino@canonical.com>
diff --git a/requirements.txt b/requirements.txt
index 31621dd..3ba81fe 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -39,7 +39,7 @@
     # via kubernetes
 idna==3.4
     # via requests
-juju==3.0.0
+juju==2.9.42.4
     # via -r requirements.in
 jujubundlelib==0.5.7
     # via theblues