Fetch only reclass-system as only one expected submodule

PROD-34108

Change-Id: Ie25deb27e83447d9aba60dd285a3c39be70687ba
diff --git a/upgrade-mcp-release.groovy b/upgrade-mcp-release.groovy
index 877a4bc..68df61b 100644
--- a/upgrade-mcp-release.groovy
+++ b/upgrade-mcp-release.groovy
@@ -456,7 +456,7 @@
                 if (updateClusterModel) {
                     common.infoMsg('Perform: UPDATE_CLUSTER_MODEL')
                     def dateTime = common.getDatetime()
-                    salt.cmdRun(venvPepper, 'I@salt:master', "cd /srv/salt/reclass/ && git submodule foreach git fetch")
+                    salt.cmdRun(venvPepper, 'I@salt:master', "cd /srv/salt/reclass/classes/system && git fetch")
                     salt.cmdRun(venvPepper, 'I@salt:master', "cd /srv/salt/reclass/classes/cluster/$cluster_name && " +
                         "grep -r --exclude-dir=aptly -l 'mcp_version: .*' * | xargs --no-run-if-empty sed -i 's|mcp_version: .*|mcp_version: \"$targetMcpVersion\"|g'")
                     // Do the same, for deprecated variable-duplicate