.zuul: Bump timeout of system tests from 20 to 25 minutes

The new additions to the system tests makes them take longer to run,
and was causing them to timeout.

containers#689
containers#787

.zuul.yaml

@@ -12,7 +12,7 @@
 - job:
     name: system-test-fedora-33
     description: Run Toolbox's system tests in Fedora 33
-    timeout: 1200
+    timeout: 1500
     nodeset:
       nodes:
         - name: ci-node-33
@@ -23,7 +23,7 @@
 - job:
     name: system-test-fedora-34
     description: Run Toolbox's system tests in Fedora 34
-    timeout: 1200
+    timeout: 1500
     nodeset:
       nodes:
         - name: ci-node-34
@@ -34,7 +34,7 @@
 - job:
     name: system-test-fedora-rawhide
     description: Run Toolbox's system tests in Fedora Rawhide
-    timeout: 1200
+    timeout: 1500
     nodeset:
       nodes:
         - name: ci-node-rawhide