[jenkins] Change triqs branch to 3.2.x

Jenkinsfile

@@ -4,7 +4,7 @@ def dockerName = projectName.toLowerCase();
 /* which platform to build documentation on */
 def documentationPlatform = "ubuntu-clang"
 /* depend on triqs upstream branch/project */
-def triqsBranch = env.CHANGE_TARGET ?: env.BRANCH_NAME
+def triqsBranch = "3.2.x"
 def triqsProject = '/TRIQS/triqs/' + triqsBranch.replaceAll('/', '%2F')
 /* whether to keep and publish the results */
 def keepInstall = !env.BRANCH_NAME.startsWith("PR-")